Schematic Editor

To place a symbol in your schematic, use the button or the A hotkey. The Choose Symbols dialog appears and lets you select a symbol to add. Symbols are grouped by symbol library.

By default, only the symbol/library name and description columns are shown. Additional columns can be added by right-clicking the column header and selecting Select Columns.

The Choose Symbol dialog filters symbols by name, keywords, description, and all additional symbol fields according to what you type into the search field. You can choose to sort search results alphabetically or by best match by clicking on the button.

Some advanced filters are available:

If the symbol specifies a default footprint, this footprint will be previewed in the lower right. If the symbol includes footprint filters, alternate footprints that satisfy the footprint filters can be selected in the footprint dropdown menu at right.

After selecting a symbol to place, the symbol will be attached to the cursor. Left clicking the desired location in the schematic places the symbol into the schematic. Before placing the symbol in the schematic, you can rotate it, mirror it, and edit its fields, by either using the hotkeys or the right-click context menu. These actions can also be performed after placement.

If the Place repeated copies option is checked, after placing a symbol KiCad will start placing another copy of the symbol. This process continues until the user presses Esc.

For symbols with multiple units, if the Place all units option is checked, after placing the symbol KiCad will start placing the next unit in the symbol. This continues until the last unit has been placed or the user presses Esc.

A power symbol is a symbol representing a connection to a power net. The symbols are grouped in the power library, so they can be placed using the symbol chooser. However, as power placements are frequent, the tool is available. This tool is similar, except that the search is done directly in the power library and any other library that contains power symbols.

Symbols can be moved using the Move (M) or Drag (G) tools. These tools act on the selected symbol, or if no symbol is selected they act on the symbol under the cursor.

The Move tool moves the symbol itself without maintaining wired connections to the symbol pins.

The Drag tool moves the symbol without breaking wired connections to its pins, and therefore moves the connected wires as well.

You can also Drag symbols by clicking and dragging them with the mouse, depending on the Left button drag gesture setting in the Mouse and Touchpad section of Preferences.

Symbols can also be rotated (R) or mirrored in the X (X) or Y (Y) directions.

Symbols in the schematic can be individually edited, both in terms of their properties (fields, attributes, etc.) and in terms of their pins and graphics. Editing a symbol in the schematic only affects that particular instance of the symbol; it does not affect any other copies of that symbol in the schematic, and it does not affect the library symbol.

To edit the properties of a symbol in the schematic, open its properties dialog (E). You can also double-click the symbol.

The Symbol Properties window displays all the fields of a symbol in a table. New fields can be added, and existing fields can be deleted, edited, reordered, moved, or resized. Fields can be arbitrarily named, but names beginning with ki_, e.g. ki_description, are reserved by KiCad and should not be used for user fields. All symbol fields will be added to the symbol’s corresponding footprint when the PCB is updated from the schematic.

Each field’s name and value can be visible or hidden, and there are several formatting options: horizontal and vertical alignment, orientation, position, font, text color, text size, and bold/italic emphasis. Field autoplacement can also be enabled on a per-field basis. The displayed position is always indicated for a normally displayed symbol (no rotation or mirroring) and is relative to the anchor point of the symbol.

Several fields have special behavior:

Symbols have several attributes that affect how the symbols are treated by other parts of KiCad.

To edit the symbols’s form, i.e. its pins and graphics, you need to use the symbol editor. There are two buttons for opening a symbol in the editor, depending on whether you want to edit a single copy of a symbol in the schematic or a symbol’s source copy in the library.

The Update Symbol from Library…​ button is used to update the schematic’s copy of the symbol to match the copy in the library. The Change Symbol…​ button is used to swap the current symbol to a different symbol in the library. These functions are described later.

The Simulation Model…​ button opens the Simulation Model Editor for specifying the symbol’s behavior in SPICE simulations.

Symbol pins can have alternate pin functions defined for them. Alternate pin functions allow you to select a different name, electrical type, and graphical style for a pin when a symbol has been placed in the schematic. This can be used for pins that have multiple functions, such as microcontroller pins.

Alternate pin functions are selected once a symbol has been placed in the schematic. The pin function is selected in the Pin Functions tab of the Symbol Properties dialog. Alternate definitions are selectable in the dropdown in the Alternate Assignment column. You can also select an alternate pin by right-clicking the pin and selecting a new function from the Pin Function menu.

Pins that have alternate functions available are displayed with a small graphical indicator next to the pin name, as shown in the screenshot below. To globally show or hide these indicators, use View → Show Pin Alternate Icons.

For information on how to add alternate pin functions to symbols, see the symbol editor documentation.

When a symbol is added to the schematic, KiCad embeds a copy of the library symbol in the schematic so that the schematic is independent of the system libraries. Symbols that have been added to the schematic are not automatically updated when the library changes. Library symbol changes are manually synced to the schematic so that the schematic does not change unexpectedly.

To update symbols in the schematic to match the corresponding library symbol, use Tools → Update Symbols from Library…​, or right click a symbol and select Update Symbol…​. You can also access the tool from the symbol properties dialog.

The top of the dialog has options to choose which symbols will be updated:

The middle of the dialog has options to control what parts of the symbol will be updated. On the left, you can select which fields will be modified (updated or reset). On the right, you can select how to update those fields:

The bottom of the dialog displays messages describing the update actions that have been performed, with filters for which types of messages to display (errors, warnings, actions, and/or infos).

To change an existing symbol to a different symbol, use Edit → Change Symbols…​, or right click an existing symbol and select Change Symbol…​. This dialog is also accessible from the symbol properties dialog.

The options for the Change Symbols dialog are very similar to the Update Symbols from Library dialog.

Another way to swap existing symbols for new ones is to use Tools → Edit Symbol Library Links…​. This dialog contains a table of every symbol in the design, grouped by current library symbol. By choosing a new symbol in the New Library Reference column, you can make all instances of the existing symbol instead point to the new symbol. If the Update symbol fields from new library option is used, the contents of the existing symbols' fields will be updated to match the new symbols' fields.

The Map Orphans button attempts to automatically remap orphaned symbols to symbols with the same name in an active library. For example, if there is a symbol with the current library reference mylib:symbol123, but the mylib library cannot be found, the Map Orphans button will attempt to find a symbol named symbol123 in any of the libraries that are present. This button is only enabled if orphaned symbols are present in the schematic (see the legacy schematics section).

This dialog is primarily useful for managing symbols that appear in multiple libraries, when you want to switch from one library to another. For example, if a schematic uses symbols that are in both a global library and a project-specific library, the Symbol Library References dialog could be used to switch between using the global symbols or the equivalent project-specific symbols. It does not have features for fine-grained control of how fields are updated; for that, use the Change Symbols dialog.

When a symbol in a schematic diverges from the corresponding symbol in the original symbol library, you can use the Compare Symbol with Library tool to inspect the differences between the two versions of the symbol. Run the tool using Inspect → Compare Symbol With Library.

The Summary tab shows the name of the symbol, including its library and schematic reference designator, and provides a list of the differences between the schematic and library versions of the symbol.

The Visual tab shows a visual comparison of the schematic and library versions of the symbol. This can be used as a visual diff tool.

By default, the comparison displays both versions of the symbol superimposed on each other. To see the changes more easily, you can drag the slider at the bottom of the tab to the right to emphasize the library version of the symbol in the superimposed view (making the schematic version of the symbol more transparent) or drag it to the left to emphasize the schematic version (making the library version more transparent). At the far right and left ends of the slider, the schematic and library versions of the symbol, respectively, are fully hidden. It may be helpful to drag the slider back and forth to see the changes more clearly.

You can press the A/B button, or use the / hotkey, to quickly toggle back and forth between the schematic and library versions.

The screenshot above shows a visual comparison with the schematic version of the symbol deemphasized. You can see a partially transparent pin 5 (from the schematic version of the symbol) is in a different location than the fully opaque pin 5 (from the library symbol). This indicates that the pin was moved in either the schematic or library version of the symbol.

The Symbol Fields Table allows you to view and modify field values for all symbols in a spreadsheet interface. You can open the Symbol Fields Table with the button.

Cells are navigated with the arrow keys, or with Tab / Shift+Tab to move right / left and Enter to move down, respectively.

A range of cells can be selected by clicking and dragging. The whole range of selected cells will be copied (Ctrl+C) or pasted into (Ctrl+V) on a copy or paste action. Copying a range of cells from the table can be useful for creating a BOM. More details of copying and pasting cells are described below.

Any symbol field can be shown or hidden using the Show checkboxes on the left or by right-clicking on the header of the table. New symbol fields can be added using the button; a field with that name will be added to every symbol. Each field can have its own label, which doesn’t have to be the same as the field name, and is used as the column header. Fields can be renamed with the button or deleted with the button.

Similar symbols can optionally be grouped by any symbol field using the Group By checkboxes. Symbols are grouped into a single row in the table if all of their Group By fields are identical. The grouped row can be expanded to show the individual symbols by clicking the arrow at the left of the row. The Group Symbols checkbox enables or disables symbol grouping, and the button recalculates groupings.

Presets are available to configure the list of fields. Presets store which fields are displayed, which fields are used for grouping, and the column order. You can create and save your own presets or use one of several default presets. Custom presets can be deleted in this dialog or in the Schematic Setup dialog.

Symbols can be filtered by reference designator using the Filter textbox at the top. The filter supports wildcards: * matches any number of any characters, including none, and ? matches any single character. You can also change the display scope, showing only symbols in the current sheet, the current sheet and all of its subsheets, or the entire project. Symbols with the DNP (do not populate) attribute set can be optionally excluded by checking the Exclude DNP box.

You can cross-probe from this dialog by selecting a row in the table. Depending on the Cross-probe action setting at the bottom of the dialog, this can highlight the corresponding symbol in the schematic, select the corresponding symbol in the schematic, or do nothing. The selection action can also select the symbol’s footprint in the board editor, depending on the PCB Editor cross-probing settings.

The Symbol Fields Table is also a bill of materials tool. You can use the Export button to save the symbol fields to an external file. The fields are exported to the BOM exactly as they are currently shown in the spreadsheet view. File format settings are configured in the Export tab. For more information about exporting a BOM, see the BOM tool documentation.

When auto-annotation is enabled, symbols will be automatically annotated when they are added to the schematic. You can enable auto-annotation by checking the Automatically annotate symbols checkbox in the Schematic Editor → Annotation Options pane in Preferences. Auto-annotation can also be toggled using the button in the left toolbar.

When multiple symbols are added simultaneously, they are annotated according to the Order setting, sorted by either X or Y position.

The Numbering option sets the starting number for new reference designators. This can be the lowest available number, or a number based on the sheet number.

For more information about annotation options, see the documentation for the Annotation tool.

The Annotation tool automatically assigns reference designators to symbols in the schematic. To launch the Annotation tool, click the button in the top toolbar.

The tool provides several options to control how symbols are annotated.

Scope: Selects whether annotation is applied to the entire schematic, to only the current sheet, or to only the selected symbols. If the Recurse into subsheets option is selected, symbols in subsheets of the selected scope will be reannotated; otherwise symbols in subsheets will not be reannotated. For example, if Recurse into subsheets and Selection only selected, symbols in any selected subsheets will be reannotated.

Options: Selects whether annotation should apply to all symbols and reset existing reference designators, or apply only to unannotated symbols.

Order: Chooses the direction of numbering. If symbols are sorted by X position, all symbols on the left side of a schematic sheet will be lower numbered than symbols on the right side of the sheet. If symbols are sorted by Y position, all symbols on the top of a sheet will be lower numbered than symbols at the bottom of the sheet.

Numbering: Selects the starting point for numbering reference designators. The lowest unused number above the starting point is picked for each reference designator. The starting point can be an arbitrary number (typically zero), or it can be the sheet number multiplied by 100 or 1000 so that each part’s reference designator corresponds to the schematic page it is on.

The Clear Annotation button clears all reference designators in the selected scope.

Annotation messages can be filtered with the checkboxes at the bottom or saved to a report using the Save…​ button.

Wires are used to directly establish electrical connections between two points. To establish a connection, a segment of wire must be connected by its end to another segment or to a pin. Only wire ends create connections; if a wire crosses the middle of another wire, a connection will not be made.

Unconnected wire ends have a small square that indicates the connection point. The square disappears when a connection is made to the wire end. Unconnected pins have a circle, which also disappears when a connection is made.

Labels are used to assign net names to wires and pins. Wires with the same net name are considered to be connected, so labels can be used to make connections without drawing direct wire connections.

A net can only have one name. If two different labels are placed on the same net, an ERC violation will be generated. Only one of the net names will be used in the netlist. The final net name is determined according to the rules described below.

There are three types of labels, each with a different connection scope.

Buses are a way to group related signals in the schematic in order to simplify complicated designs. Buses can be drawn like wires using the bus tool , and are named using labels the same way signal wires are.

In the following schematic, many pins are connected to buses, which are the thick blue lines in the center.

Power symbols are symbols that are conventionally used to represent a connection to a power net, such as VCC or GND. Power symbols are virtual: they do not represent a physical component on the PCB.

In addition to being a visual indicator that the attached net is a power rail, power symbols make global connections: two power symbols with the Value connect to each other anywhere in the schematic, regardless of sheet. The power symbol’s Value field determines the name of the attached net.

In the figure below, power symbols are used to connect the positive and negative terminals of the capacitors to the VCC and GND nets, respectively.

In the KiCad standard library, power symbols are found in the power library, but power symbols can be created in any library. Creating custom power symbols is described in the symbol editor documentation. Instead of making a new symbol, you can also modify an existing power symbol in the schematic: changing its Value field will change the net the power symbol connects to.

Every net in the schematic is assigned a name, whether that name is specified by the user or automatically generated by KiCad.

When multiple labels are attached to the same net, the final net name is determined in the following order, from highest priority to lowest:

If there are multiple labels of one type attached to a net, the names are sorted alphabetically and the first is used.

If a net travels through multiple sheets of a hierarchy, it will take its name from the highest level of the hierarchy where it has a hierarchical label or local label. As usual, local labels take priority over hierarchical labels.

If none of the label types above are attached to a net, the net’s name is automatically generated based on the connected symbol pins.

Two PWR_FLAG symbols are visible in the screenshot above. They indicate to ERC that the two power nets VCC and GND are actually connected to a power source, as there is no explicit power source such as a voltage regulator output attached to either net.

Without these two flags, the ERC tool would diagnose: Error: Input Power pin not driven by any Output Power pins.

The PWR_FLAG symbol is found in the power symbol library. The same effect can be achieved by connecting any power output pin to the net.

No-connection flags () are used to indicate that a pin is intentionally unconnected. These flags prevent "unconnected pin" ERC warnings for pins that are intentionally unconnected. Also, while symbol pins that are stacked on top of each other are normally connected to the same net, if a no-connection flag is added to the stacked pins they will instead be connected to separate nets.

Note that no-connection flags are distinct from the "unconnected" symbol pin type, although they both prevent "unconnected pin" ERC warnings on the pin in question and prevent stacked pins from connecting to each other.

When the power pins of a symbol are visible, they must be connected, as with any other signal. However, symbols are sometimes drawn with hidden power input pins, which are connected implicitly. KiCad automatically connects invisible pins with type Power Input to a global net with the same name as the pin. For example, if a symbol has a hidden power input pin named VCC, this pin will be globally connected to the VCC net on all sheets. This kind of implicit connection is not recommended in new designs.

Net classes are managed in the Net Classes panel of the Schematic Setup dialog.

The top pane lists the net classes that exist in the design. The Default net class always exists, and you can add additional net classes with the button or remove the selected net class with the button.

Net classes can be moved up and down in priority order with the and buttons. Note that the Default net class will always be the lowest priority net class and can therefore not be moved.

Each net class can have unique graphic properties that determine how wires of that net class are displayed in the schematic. Wire and bus thicknesses, color, and line style (solid, dashed, dotted, etc.) can all be adjusted. Setting the color to transparent will use the theme’s default wire/bus color for the net class, which is configurable in Preferences. By default any color that is configured for a net class controls the color is used to draw wires in that net class. If the Highlight netclass colors setting is enabled in the Display Options section of the Schematic Editor preferences, this color will instead be used to draw a highlight around wires in that netclass, and the wires themselves will always be drawn with the color scheme’s wire color.

You can also set board design rules for each net class, although the DRC fields are hidden by default. Right click the header row to show or hide additional columns. For more information about setting net class design rules, see the PCB editor documentation.

All net class parameters for user-defined net classes are optional. However, all properties belonging to the Default net class must be set. When a net has more than one net class assigned, the appropriate value for graphic properties or board design rules is taken from the highest priority assigned net class with the relevant value set. If only one net class is assigned which contains missing properties, any missing values will be taken from the Default net class.

The bottom pane lists pattern-based net class assignments. Each row has a net name pattern and a net class; nets with names that match the pattern are assigned to the specified net class. If a net matches multiple patterns, the net is assigned to all of the matching net classes. You can sort the list of net class assignment patterns by pattern or by net class name by clicking on the corresponding column header.

Pattern-based net class assignments are dynamic: when a new net is added that matches an existing pattern, it will be assigned to the associated net class automatically. Net patterns can use both wildcards (* to match any number of any characters, including none, and ? to match any character) and regular expressions. The nets that match the selected pattern are displayed to the right of the pattern list.

For example, the net* pattern matches nets named net, net1, network, and any other net name beginning with net. Because * has a slightly different meaning in a regular expression (* matches zero or more of the preceding character), the net* pattern would also match a net named ne.

Use the button to add a net class assignment pattern or the button to remove a pattern.

Instead of adding net class patterns in the Schematic Setup dialog, you can directly create net class patterns from the schematic canvas. Right click a net and select Assign Netclass…​ to bring up the Add Netclass Assignment dialog. The net class pattern is pre-filled with the name of the selected net, but the pattern can be changed if desired. All nets matching the pattern are displayed in the dialog. This method can only be used on nets with an assigned name.

As an alternative to pattern-based net class assignment, net classes can be graphically assigned to nets in the schematic using either directive labels, net labels, or rule areas.

In the image below, a directive label is used to assign signals to the 50R net class.

Directive labels are added with the button in the right toolbar. They behave like labels, except that they cannot be used to name a net. The attached net is assigned a net class according to the value of the directive’s Net Class field. The Net Class field presents a dropdown list of all the net classes that have been specified in Schematic Setup or Board Setup.

You can also type in a net class that isn’t explicitly listed in the Schematic/Board Setup priority list. Such implicit net classes can’t be assigned any design settings, like net class color or track width, but they can still be used in DRC rule queries.

If multiple Net Class fields are added to a directive label, or multiple directive labels with Net Class fields are applied to a net, all of the specified net classes are assigned to the net.

If a directive is attached to a bus, all members of the bus are assigned to the specified net class.

In addition to the associated net class, you can edit the directive’s shape (dot, circle, diamond, or rectangle), orientation, pin length, and color in the directive’s properties.

The Rule Area tool () can be used to draw a shape to which net class directives can be attached. Any wire, bus, label, or symbol pin which crosses or is inside the rule area will be assigned the net class of a net class directive attached to the rule area border. An example is shown in the image below; all wires passing through the rule area will be assigned the RAM_ADDR net class.

You can show or hide directive labels in the schematic using the View → Show Directive Labels option.

Two kinds of text can be added to schematics, which are referred to as text () and text boxes (). Both are added using their respective buttons in the right toolbar. Text boxes are similar to regular text except that they have an optional border and they automatically reflow text within that border.

Both kinds of text item support multiline text and basic formatting features, but text boxes wrap text to fit in the outline and have additional formatting options. All text has adjustable fonts, color, size, bold and italic emphasis, left and right alignment, and vertical and horizontal orientation. Text boxes additionally support horizontal centering, vertical alignment options, and colored borders and fill. You can also adjust the padding on each side of text in a text box (padding can be set using the Properties Manager, but not using the Text Box Properties dialog).

You can use a table to organize text in a tabular format. Tables have customizable borders, cell sizes, colors, and headers.

To place a table, use the button in the right toolbar. Click in the canvas to place the top left corner of the table, then click again to place the bottom right corner of the table and finish drawing the table. The bigger you draw the table, the more rows and columns will be added by default, but rows and columns can be added or deleted after the table is created.

Graphic rectangles (), circles (), arcs (), and lines () can all be added using their respective buttons in the right toolbar.

Line width, color, and style (solid, dashed, or dotted) can be configured in the properties dialog for each shape (E). Rectangles, circles, and arcs can also have a fill color set and have their outlines removed.

Setting a shape’s line width to 0 uses the schematic default line width, which is configurable in Schematic Setup. Spacing for line dashes is also configurable there. Removing a line or fill color uses the color theme’s graphics color, which is configurable in Preferences.

Like wires, graphic lines obey the line drawing mode setting (90 degree, 45 degree, or free angle), which you can set using the toggle buttons on the left toolbar (, , and , respectively). Shift+Space cycles through the modes.

As with PCB tracks, the / hotkey switches line posture.

KiCad supports inserting images into the schematic. These are purely for reference during the design process and play no electrical role.

To add a reference image, use the button on the right toolbar and select the desired reference image file. Click in the canvas to place the image.

Once the image has been added to the canvas, you can reposition it using the move tool (M) or by dragging it in the canvas. You can scale it by dragging the editing handles at the corners of the image. The image is scaled around its reference point; in other words, the reference point is the point in the image that always stays in the same position in the canvas, no matter how the image is scaled. The reference point is shown as a fifth editing handle. Initially it is at the center of the image, but you can reposition the reference point by dragging it in the canvas.

You can also reposition or scale the image in its properties dialog (E). You can set the image’s exact Position X and Y in the General tab, and set an exact Scale factor in the Image tab. You can also Convert to Greyscale if you wish. Position and scale in this dialog are relative to the center of the image, not its interactive reference point.

Properties of text and graphics, including symbol fields, can be edited in bulk using the Edit Text and Graphic Properties dialog (Edit → Edit Text and Graphic Properties…​). The tool can also modify visual properties of wires and buses.

The drawing sheet’s title block is edited with the Page Settings tool (). You can also open this tool by double clicking anywhere on any part of the drawing sheet.

Each field in the title block can be edited, as well as the paper size and orientation. If the Export to other sheets option is checked for a field, that field will be updated in the title block of all sheets, rather than only the current sheet.

You can set the date to today’s or any other date by pressing the left arrow button next to Issue Date. Note that the date listed in the schematic title block is not automatically updated. It is only updated when changed in this dialog.

A drawing sheet file can also be selected to replace the default drawing sheet. When choosing a drawing sheet, you can enable the Embed File checkbox in the file browser to embed the drawing sheet in the schematic instead of referencing an external file. This means the schematic will appear the same when it is opened on another computer that does not have the drawing sheet file available at the same external file path. For more information, see the embedded files documentation.

The sheet number (Sheet X/Y) is automatically updated, but sheet page numbers can also be manually set using Edit → Edit Sheet Page Number…​.

You can quickly add wires, labels, or no-connection markers to a selection of pins using the Pin Helpers tools in the right-click context menu. This can help you quickly break out unconnected pins from a symbol or hierarchical sheet. By selecting Pin Helpers → Wire, the wire tool will begin drawing a wire from all selected pins at once. If you select No Connect, no-connection markers will be added to the end of each selected pin. And if you choose Net Label, Hierarchical Label, or Global Label, a label of the respective type will be placed at the end of each selected pin. Each label’s name will be set to the corresponding pin name. The new labels will remain selected, so you can easily move them away from the symbol using M or G, depending on whether you wish to maintain a wired connection between the pins and the labels.

Existing labels and text objects can be changed to another type of label or text by right clicking the object(s) and selecting the target object type from the Change To submenu. The allowed types for source and target objects are local labels, global labels, hierarchical labels, directive labels, text objects, and text boxes. The value of the original object is preserved in the resulting object: when a text object is converted to a label, the label’s value (net name) will be the original text, and vice versa.

You can swap the position of two selected objects using the Swap command (S; also available in the right-click context menu). This works on symbols, labels, and graphical items. The first object is assigned the location and rotation of the second object, and vice versa. If there are more than two objects selected, the locations are cycled: the last object gets the position of the first object, the first object gets the location of the second, and so on.

The formatting panel contains settings for the appearance of symbols, text, labels, graphics, and wires.

Symbol unit notation sets how each unit of a multi-unit symbol is referred to in its reference designator. By default, a different letter for each unit is appended to the reference designator with no separator, for example U1B for the second unit of symbol U1, but this can be changed. Numbers can be used instead of letters, and various separators can be used between the symbol designator and the unit identifier (., -, _, or none).

Default text size sets the default text height used by the text, text box, and label tools. Overbar offset ratio controls the vertical spacing between text and an overbar (~{}) over that text, as a ratio of the text height. Label offset ratio controls the vertical spacing between a local label’s text and the attached wire, relative to the label’s text size. This also affects the spacing between symbol pins and their pin number. Global label margin ratio defines the size of the box around a global label, relative to the global label’s text size. Increasing the margin may be useful to avoid overlapping text with overbars (~{}) or letters with descenders, but this may cause closely packed global labels to overlap with each other.

Default line width sets the default line width for symbol graphics, if the symbol does not override the default line width. Pin symbol size scales symbol pin graphic style annotations, such as the bubble on an inverted pin.

Junction dot size sets the schematic’s default wire junction dot size. The default size can be overridden by editing an individual junction dot’s properties. Connection width specifies the grid size used for the Symbol pin or wire end off connection grid ERC check. Schematics typically use a 50 mil grid for electrical connections, so this should usually remain set at 50 mils.

The Operating Point Overlay settings configure how operating point simulation results are displayed on the schematic canvas. The significant digits settings control the number of significant digits printed on voltage and current overlays. The range settings control the units used to display voltage and current measurements.

Show inter-sheet references enables or disables the display of inter-sheet references, which are a list of page numbers next to a global labels that link to other places in the schematic where the same global label appears. Show own page reference controls whether the current page is included in the list of page numbers. Standard and abbreviated determine whether to display the complete list of page numbers or only the first and last page numbers. The prefix and suffix fields add optional characters before and after the list of page numbers. In the image of an inter-sheet reference below, a prefix and suffix of [ and ], respectively, have been added.

Dashed line appearance is controlled in the Formatting section. Dash length controls the length of dashes, while Gap length controls the spacing between dashes and dots. The dash and gap lengths are relative to the line width: a gap length of 2 means twice the width of the line.

Field name templates are empty symbol fields that are automatically added to all symbols in the schematic. These can be useful when every symbol in the schematic needs additional fields beyond the fields that are defined in the library symbols, for example a field for the manufacturer’s part number.

Template fields can be set as visible or invisible, and can also be set as URL fields.

Field name templates that are defined in schematic setup apply only to the current project. Field name templates can also be defined in Preferences, which apply to all projects edited on your computer.

BOM presets are saved configurations for the Symbol Fields Table and BOM export tool. There are two types of presets. BOM presets configure which fields are displayed in the symbol fields table, which order they are displayed in, and how they are used to group symbols. These fields are also directly used in the BOM output. BOM formatting presets configure the output BOM file format, including which separator characters are used to separate fields. Both types of presets are created in the Symbol Fields Table, but can are listed and can be deleted here.

The Violation Severity panel lets you configure what types of ERC messages should be reported as Errors, Warnings, or ignored.

The Pin Conflicts Map allows you to configure connectivity rules to define electrical conditions for errors and warnings based on what types of pins are connected to each other. For example, by default an error is produced when an output pin is connected to another output pin.

These panels are explained in more detail in the ERC section.

The Net Classes panel allows you to manage net classes for the project and assign nets to net classes with patterns. Managing net classes in this panel is equivalent to managing them in the Board Setup dialog. Nets can also be assigned to net classes in the schematic using graphical assignments with net class directives or net labels.

Pattern-based net class assigment is explained in more detail in the net classes section.

The Bus Alias Definitions panel allows you to create bus aliases, which are names for groups of signals in a bus. For more information about bus aliases, see the bus alias documentation.

Text replacement variables can be created in the Text Variables section. These variables allow you to substitute the variable name for any text string. This substitution happens anywhere the variable name is used inside the variable replacement syntax of ${VARIABLENAME}.

For example, you could create a variable named VERSION and set the text substitution to 1.0. Now, in any text object on the PCB, you can enter ${VERSION} and KiCad will substitute 1.0. If you change the substitution to 2.0, every text object that includes ${VERSION} will be updated automatically. You can also mix regular text and variables. For example, you can create a text object with the text Version: ${VERSION} which will be substituted as Version: 1.0.

Text variables can also be created in Board Setup. Text variables are project-wide; variables created in the schematic editor are also available in the board editor, and vice versa.

There are also a number of built-in system text variables.

External files can be embedded within a schematic. Embedding a file stores a copy of the file inside the schematic file. The design can then refer to the embedded copy of the file instead of the external file, which makes the project more portable as it doesn’t rely on an external file. Fonts, datasheets, drawing sheets, SPICE models, and footprint 3D models can be embedded and used within KiCad. Other arbitrary files can also be embedded to store them in the project for later export, but they are not used by any KiCad functionality. Files embedded in a schematic necessarily increase the schematic’s file size, although files are compressed before being embedded to minimize the space required.

Embedded files are managed in the Embedded Files section of Schematic Setup. All files embedded in a schematic are shown here. To embed a file inside a schematic, click the button and select the file. The file is then embedded inside the schematic and is listed in the embedded files list along with its embedded reference. The embedded reference is a unique identifier for the embedded file that begins with kicad-embed://. You can use the embedded reference elsewhere in the Schematic Editor to refer to the embedded file as if it were an external file path. You can copy the embedded reference by right clicking and selecting Copy Embedded Reference. To remove an embedded file, click the button. Any remaining links to the removed file will become invalid.

To embed any fonts used in a schematic, check the Embed fonts checkbox. All fonts used in the schematic will be embedded, so text using that font can be edited on any computer regardless of whether the font file is installed.

You can also embed files in a library symbol. Such files will be available within the symbol, but not within the larger schematic or in other symbols. Files embedded in a symbol are deduplicated when the symbol is added to a schematic: if a file is embedded in a symbol, and multiple instances of that symbol are added to the schematic, only one copy of the file will be embedded, and all of the symbol instances will refer to the same embedded file.

As an example, to embed a datasheet in a project and use it within several symbols, you could embed the datasheet using the schematic setup dialog, copy the internal reference, and paste the internal reference into the datasheet field of each symbol that uses that datasheet. Each symbol would then have a portable reference to the embedded datasheet. Alternatively, you could embed the datasheet within the library symbol. In this case, each symbol will already have the datasheet embedded when the symbol is added to a schematic. A more convenient way to achieve the same thing, however, is to open the symbol’s properties dialog, browse for a datasheet file, and enable the Embed File option in the file browser. Again, this could be done for a symbol in the schematic or for a symbol in the source symbol library.

Files can also be embedded in boards.

You can import some or all of the schematic setup from an existing schematic. This allows you to choose a schematic to use as a template and select which settings to import.

To import settings, click the Import Settings from Another Project…​ button at the bottom of the Schematic Setup dialog and then choose the .kicad_sch file you want to import from. Select which settings you want to import and the current settings will be overwritten with the values from the chosen schematic.

The settings that are available to import are:

Modern versions of KiCad can open schematics created in versions prior to KiCad 6.0, but the cache library file (<projectname>-cache.lib) must be present to load the schematic correctly.

Since version 6.0, KiCad stores all symbols used in a project in the schematic. This means that you can open a schematic made in KiCad 6.0 or later on any computer, even if the libraries used in the project are not installed or have changed. Modern KiCad schematic files use the .kicad_sch extension.

Prior to version 6.0, KiCad did not store symbols in the schematic. Instead, KiCad stored references to the symbols and their libraries. It also stored a copy of every symbol used by the project in a separate cache library file (<projectname>-cache.lib). As long as the cache library was included with the project, the project could be distributed without the system library files, because KiCad could load any needed symbols from the cache library as a fallback if the libraries referenced in the schematic were missing. Legacy KiCad schematic files use the .sch extension.

When you open a legacy schematic, KiCad will look in the cache library to find all of the symbols used in the schematic in the cache library. When you save the legacy schematic, KiCad will save it as a new file in the modern schematic format (.kicad_sch), with the necessary symbols embedded in the schematic itself. The original legacy schematic and the cache library will remain, unmodified, but they are no longer necessary once the schematic has been saved in the modern format.

When you open a legacy schematic, KiCad may display the Project Rescue Helper dialog. This means that one or more symbols in the cache library do not match the corresponding symbol in the external library. The dialog helps you "rescue" symbols from the cache library into your schematic, if desired. You can also open the rescue dialog at any time using Tools → Rescue Symbols…​. The cache library file must be present in order to use the rescue tool.

The rescue dialog lists all symbols that don’t match between the cache library and the external symbol library. The discrepancy can be because:

For each symbol in the list, selecting the symbol displays the reference designator and value for each instance of the symbol, and shows a visual preview of the symbol. If a corresponding symbol exists in the system symbol library, the dialog shows both copies of the symbol for comparison. If the symbol only exists in the cache library, the dialog only shows the cached symbol.

In this example, the project originally used a diode with the cathode facing left, but the library now contains one with the cathode facing right. This change would break the design, so it would be important to use the cached symbol as the original designer intended.

Pressing Rescue Symbols here will cause the selected symbols from the cache library to be saved into a special rescue library (<projectname>-rescue.kicad_sym). The corresponding symbols in the schematic will be updated to use the newly rescued symbols. Any unselected symbols will not be rescued, but their symbol linkage can be updated in the schematic later.

Alternatively, pressing Skip Symbol Rescue will exit the dialog without rescuing any symbols. KiCad will use the versions of the symbols found in the external libraries. You can run the rescue function again with Tools → Rescue Symbols…​, or manually edit symbol linkage in the symbol’s properties.

If you would prefer not to see this dialog, you can press Never Show Again. This has the same effect as pressing Skip Symbol Rescue for the current schematic and all future schematics.

If a symbol in a legacy schematic cannot be found in either the cache library or the external library, KiCad cannot rescue that symbol. A placeholder symbol is inserted into the schematic in its place, as shown below.

You can attempt to remap these orphaned symbols using the Change Symbols or Edit Symbol Library Links dialogs, but either option may require manual corrections to the schematic. These tools are explained in more detail in the Updating and exchanging symbols section.

Modern versions of KiCad can open schematics created in versions prior to KiCad 5.0, but you will need to go through a symbol remapping process to open the schematic without losing symbol information.

Since version 5.0, KiCad schematics refer to specific symbols using both the symbol and library name. Even if multiple libraries each contain a symbol with the same name, the designer’s intended symbol is unambiguously specified.

Prior to version 5.0, KiCad schematics stored only the symbol name, not the library name. Symbols in the schematic were indirectly mapped back to the original library by searching through the project’s library list for a matching symbol. When you open a pre-5.0 schematic, KiCad will attempt to automatically "remap" the symbols so that each bare symbol name is replaced with a fully-specified symbol library and symbol name pair. The original schematics will be backed up in a rescue-backup folder.

You can skip the automatic remapping, but you will need to remap the symbols yourself using the Change Symbols dialog. You can also re-run the Remap Symbols tool using Tools → Remap Legacy Library Symbols…​.

Electrical connections between sheets are made with labels. There are several kinds of labels in KiCad, each with a different connection scope.

After placing hierarchical labels within the subsheet, matching hierarchical sheet pins can be added to the subsheet symbol in the parent sheet. You can then make connections to the hierarchical pins with wires, labels, and buses. Hierarchical sheet pins in a subsheet symbol are connected to the matching hierarchical labels in the subsheet itself.

For every hierarchical label in the subsheet, add the corresponding hierarchical pin onto the sheet symbol by clicking the button in the right toolbar, then clicking on the sheet symbol. A sheet pin for the first unmatched hierarchical label will be attached to the cursor, where it can be placed anywhere along the border of the sheet symbol. Clicking again with the tool will continue to add additional sheet pins until all of the hierarchical labels in the subsheet have a matching sheet pin on the sheet symbol. Sheet pins can also be imported by selecting Place Sheet Pin in a sheet symbol’s right-click context menu.

You can edit the properties of a sheet pin in the Sheet Pin Properties dialog. Open this dialog by double-clicking a sheet pin, selecting a sheet pin and using the E hotkey, or right-clicking a sheet pin and selecting Properties…​.

The sheet pin’s name can be edited in the textbox or by selecting from the dropdown list of hierarchical labels in the subsheet. A sheet pin’s name has to match the corresponding hierarchical label in the subsheet, so if you change a pin name you must change the label name as well.

Shape changes the shape of the sheet pin, and has no electrical effect. It can be set to Input, Output, Bidirectional, Tri-state, or Passive. The pin’s font, text size, color, and emphasis (bold or italic) can also be changed.

Another way to manage the connections between hierarchical labels and sheet pins is to use the Sync Sheet Pins tool. Launch this tool using the button in the right toolbar or with Sync Sheet Pins in a sheet symbol’s right click context menu.

This dialog shows the hierarchical labels and hierarchical sheet pins for each hierarchical sheet. If the tool was launched from the context menu of a sheet symbol, only one tab will be available, with the labels and sheet pins for that specific sheet. If the tool was started globally, i.e. with the button or with Place → Sync Sheet Pins, a tab will be shown for each hierarchical sheet.

The icon in each tab indicates whether the hierarchical sheet pins on the sheet symbol are correctly matched with the hierarchical labels inside the sheet. If the tab has a icon, then there is a hierarchical label in the sheet without a matching sheet pin, or a sheet pin without a corresponding hierarchical label, or both. If the tab has a icon, then the hierarchical labels and hierarchical sheet pins are matched up correctly. Sheet pins and labels are considered matching if they have the same name and the same graphic shape (input, output, bidirectional, tri-state, or passive).

The column on the left lists sheet pins for the current sheet that do not have a corresponding hierarchical label in the sheet. The middle column lists hierarchical labels in the current sheet that do not have a corresponding hierarchical sheet pin on the sheet symbol. The right column lists pairs of matching sheet pins and hierarchical labels. The name of each pin or label is shown along with its graphic shape.

If you click the Add Hierarchical Labels button, new hierarchical labels corresponding to the selected sheet pins will be created for you to place sequentially in the sheet. The selected sheet pins are then removed from the left column and added to to the right column for matching sheet pins and labels. Clicking Delete Sheet Pins will delete the selected sheet pins from the sheet symbol.

If you click the Add Sheet Pins button, new sheet pins corresponding to the selected hierarchical labels will be created for you to place on the sheet symbol. The hierarchical labels are then removed from the middle column and added to the right column for matching sheet pins and labels. Clicking Delete Hierarchical Labels will delete the selected hierarchical labels from inside the sheet.

Clicking the button will match the selected sheet pin and hierarchical label by renaming the sheet pin to match the hierarchical label’s name. Clicking the button will do the opposite, matching the selected sheet pin and hierarchical label by renaming the label to match the sheet pin.

Clicking the button will unmatch a matched pair, moving both the sheet pin and the hierarchical label back to their respective unmatched columns. The unmatched sheet pin and hierarchical label can then be edited or rematched as desired.

Any changes made in the Sync Sheet Pins dialog are applied immediately, before the dialog is closed. To cancel a change made in the Sync Sheet Pins dialog, use Undo.

An example of a simple hierarchy is the video demo project included with KiCad. The root sheet contains seven unique subsheets, each with hierarchical labels and sheet pins linking the sheets to each other in the root sheet. Two of the subsheet symbols are shown below.

The complex_hierarchy demo project is an example of a complex hierarchy. The root sheet contains two subsheet symbols, which both refer to the same sheet file (ampli_ht.kicad_sch). This allows the design to include two copies of the same amplifier circuit. Although the two sheet symbols refer to the same filename, the sheet names are unique (ampli_ht_vertical and ampli_ht_horizontal). Inside each subsheet the circuits are identical except for the reference designators, which as always are unique.

This project contains no sheet pin connections. The only connections between the root sheet and the subsheets are global power connections made with power symbols. However, sheets in a complex hierarchy could include sheet pin connections if appropriate for the design.

The flat_hierarchy demo project is an example of a flat hierarchy. The root sheet contains two unique subsheet symbols with no hierarchical sheet pins. The root sheet in this project does nothing except hold the subsheets, and the subsheets are used only as additional pages in the schematic.

There are three errors in the screenshot above.

Selecting an ERC marker displays a description of the violation in the message pane at the bottom of the window.

It is common to have an "Input Power pin not driven by any Output Power pins" error on power pins, as shown in the example below, even though the power pins seem to be properly connected to a power rail. This happens in designs where the power is provided through connectors or other components that are not marked as power outputs. In these cases ERC won’t detect any Output Power pins connected to the net and will determine the Input Power pin is not driven by a power source.

To avoid this warning, connect the net to PWR_FLAG symbol on such a power net as shown in the following example. The PWR_FLAG symbol is found in the power symbol library. Alternatively, connect any power output pin to the net; PWR_FLAG is simply a symbol with a single power output pin.

Ground nets often need a PWR_FLAG as well, because voltage regulators have outputs declared as power outputs, but their ground pins are typically marked as power inputs. Therefore grounds can appear unconnected to a source unless a PWR_FLAG symbol is used.

For more information about power pins and power flags, see the PWR_FLAG documentation.

The Violation Severity panel in Schematic Setup lets you configure what types of ERC messages should be reported as Errors, Warnings, or ignored.

The Pin Conflicts Map panel in Schematic Setup allows you to configure connectivity rules to define electrical conditions for errors and warnings based on what types of pins are connected to each other. For example, by default an error is produced when an output pin is connected to another output pin.

Rules can be changed by clicking on the desired square of the matrix, causing it to cycle through the choices: allowed, warning, error.

The table below lists the electrical rules that KiCad checks and the default violation severity for each check. All severities are configurable.

You can manually trigger schematic ERC warnings or errors using special text variables. These items will appear as errors or warnings when ERC runs. This can be useful to flag items for later followup or review.

To cause an ERC violation, use the text variable ${ERC_ERROR <violation name>} or ${ERC_WARNING <violation name>} depending on whether an error or warning is desired. You can place this in a text item, text box, or field, including symbol fields, sheet fields, and label fields. When ERC runs, this will generate a ERC violation with the given violation name. These text variables resolve to an empty string in the schematic, and any text after the braces is included in the ERC violation’s description. The text variable must be placed at the start of the text object in order to trigger a violation.

For example, a text item containing ${ERC_ERROR TODO}Calculate resistor value will appear in the board as just the text "Calculate resistor value", and will generate an ERC error named "TODO" with "Calculate resistor value" in the description.

An ERC report file can be generated and saved by clicking the Save…​ button in the ERC dialog. The file extension for ERC report files is .rpt. An example ERC report file is given below.

Rather than editing the properties of each symbol individually, the Symbol Fields Table can be used to view and edit the properties of all symbols in the design in one place. This includes assigning footprints by editing the Footprint field of each symbol.

The Symbol Fields Table is accessed with Tools → Edit Symbol Fields…​, or with the button on the top toolbar.

The Footprint field behaves the same here as in the Symbol Properties window: it can be edited directly, or footprints can be selected visually with the Footprint Library Browser.

For more information on the Symbol Fields Table, see the section on editing symbol properties.

The image below shows the main window of the Footprint Assignment Tool.

The top toolbar contains the following commands:

The following table lists the keyboard commands for the Footprint Assignment Tool:

To manually associate a footprint with a component, first select a component in the component (middle) pane. Then select a footprint in the footprint (right) pane by double-clicking on the name of the desired footprint. The footprint will be assigned to the selected component, and the next component without an assigned footprint is automatically selected.

When all components have footprints assigned to them, click the OK button to save the assignments and exit the tool. Alternatively, click Cancel to discard the updated assignments, or Apply, Save Schematic & Continue to save the new assignments without exiting the tool.

The Footprint Assignment Tool allows you to store footprint assignments in an external file and load the assignments later, even in a different project. This allows you to automatically associate symbols with the appropriate footprints.

The external file is referred to as an equivalence file, and it stores a mapping of a symbol value to a corresponding footprint. Equivalence files typically use the .equ file extension. Equivalence files are plain text files with a simple syntax, and must be created by the user using a text editor. The syntax is described below.

You can select which equivalence files to use by clicking Preferences → Manage Footprint Association Files in the Footprint Assignment Tool.

Relevant environment variables are shown at the bottom of the window. When the Relative path option is checked, these environment variables will automatically be used to make paths to selected equivalence files relative to the project or footprint libraries.

Once the desired equivalence files have been loaded in the correct order, automatic footprint association can be performed by clicking the button in the top toolbar of the Footprint Assignment Tool.

All symbols with a value found in a loaded equivalence file will have their footprints automatically assigned. However, symbols that already have footprints assigned will not be updated.

The Footprint Assignment Tool contains a footprint viewer. Clicking the button in the top toolbar launches the footprint viewer and shows the selected footprint.

The top toolbar contains the following commands:

The left toolbar contains the following commands:

The tool has several options to control its behavior.

The tool has several options to control its behavior.

Select changes can also be synced from the PCB back to the schematic by exporting a CMP file from the PCB editor (File → Export → Footprint Association (.cmp) File…​) and importing it in the Schematic Editor (File → Import → Footprint Assignments…​).

Plotted PDFs can optionally have several interactive features.

The exported BOM will contain exactly the components (rows) and fields (columns) shown in the Edit tab, with the same grouping and sorting. Components with the Exclude from BOM attribute set are hidden in the Edit tab and not included in the BOM export unless the Show 'Exclude from BOM' box is checked. Components with the DNP (do not populate) attribute set can be optionally excluded from both the table in the Edit tab and the exported BOM by checking the Exclude DNP box. You can also limit the displayed components to those in the current sheet, the current sheet and all of its subsheets, or the entire schematic by adjusting the Scope settings.

Fields with the Show box checked will be included as columns in the BOM, and fields with the Group By box checked are used to group components together. Components are grouped into the same line if all of their Group By fields are identical and the Group symbols box is checked. You can set an arbitrary column name for each field and reorder columns by dragging their headers.

Presets are available to configure the list of fields. Presets store which fields are displayed, which fields are used for grouping, and the column order. You can create and save your own presets or use one of several default presets. Custom presets can be deleted in this dialog or in the Schematic Setup dialog.

The built-in presets "Grouped By Value" and "Grouped By Value and Footprint" replicate legacy BOM scripts, while "Attributes" shows only the reference and value fields and the DNP, exclude from board, exclude from simulation, and exclude from BOM attributes.

Some virtual fields are available that may be useful in BOM exports. Adding a field in the Symbol Fields Table beginning with a text variable will not create a new field in the symbols, but will create a special column in the table and BOM with auto-generated values for each component. The following variables may be especially useful for creating virtual fields in custom BOM formats:

Other text variables are also available.

The full functionality of the Edit tab, including virtual field behavior, is explained in more detail in the Symbol Fields Table documentation.

The Export tab contains settings concerning the output file format for the BOM and displays a preview of the raw BOM file output.

At the top you can specify the output file. Pressing the Export button will write the BOM to this file path. This path can contain text variables.

The settings on the left control how the BOM information is formatted in the file. You can change the delimiter between fields, the delimiter that surrounds each field, the delimiter that separates a sequence of references (e.g. the comma in R1,R3), and the delimiter for a range of references (e.g. the dash in R1-R3). If no range delimiter is given, ranges will not be used: R1-R3 will be written out as R1,R2,R3, for example, assuming , as a reference delimiter. Tabs and newlines in fields can be preserved or stripped, depending on the Keep tabs and Keep line breaks settings.

Several default format presets are available. You can select a comma-separated value (CSV) format, a tab-separated value (TSV) format, or a semicolon-separated format. You can also create and save your own presets. Custom presets can be deleted in this dialog or in the Schematic Setup dialog.

Previous versions of KiCad used external scripts to process the design information into the desired output format. This BOM generation tool is still available by selecting Tools → Generate Legacy Bill of Materials…​.

Several BOM generator scripts are included with KiCad, and users can also create their own. BOM generator scripts generally use Python or XSLT, but other tools can be used as long as you can specify a command line for KiCad to execute when running the generator.

You can select which BOM generator to use in the BOM generator scripts list. The rest of the dialog displays information about the selected generator. You can change the displayed name of the generator with the Generator nickname textbox.

The pane at right displays information about the selected script. When the generator is executed, the right pane instead displays output from the script.

The text box at the bottom contains the command that KiCad will use to execute the generator. It is automatically populated when a script is selected, but the command may need to be hand-edited for some generators. KiCad saves the command line for each generator when the BOM tool is closed, so command line customizations are preserved. For more details about the command line, see the advanced documentation.

On Windows, the BOM Generator dialog has an additional option Show console window. When this option is unchecked, BOM generators run in a hidden console window and any output is redirected and printed in the dialog. When this option is checked, BOM generators run in a visible console window, which may be necessary if the generator plugin provides a graphical user interface.

The PCB Editor can export a BOM through File → Fabrication Outputs → BOM…​. This method provides no control over the output format and does not include all symbol information, but is useful for PCB-only workflows that do not involve a schematic. In general, it is recommended to use the schematic editor’s BOM export tool instead.

Netlists are exported with the Export Netlist dialog (File→Export→Netlist…​).

KiCad supports exporting netlists in several formats: KiCad, OrcadPCB2, Allegro, PADS, CADSTAR, Spice, and Spice Model. Each format can be selected by selecting the corresponding tab at the top of the window. Some netlist formats have additional options.

Clicking the Export Netlist button prompts for a netlist filename and saves the netlist.

Custom generators for other netlist formats can be added by clicking the Add Generator…​ button. Custom generators are external tools that are called by KiCad, for example Python scripts or XSLT stylesheets. For more information on custom netlist generators, see the section on adding custom netlist generators.

Below is the schematic from the sallen_key project included in KiCad’s simulation demos.

The KiCad format netlist for this schematic is as follows:

In Spice format, the netlist is as follows:

The first time the KiCad Schematic Editor is run and the global symbol table file sym-lib-table is not found in the KiCad configuration folder, KiCad will guide the user through setting up a new symbol library table. This process is described above. You can re-run this process at any time by clicking the Reset Libraries.

Symbol libraries can only be used if they have been added to either the global or project-specific symbol library table.

Add a library either by clicking the button and selecting a library or clicking the button and typing the path to a library file. The selected library will be added to the currently opened library table (Global or Project Specific). Libraries can be removed by selecting desired library entries and clicking the button.

The and buttons move the selected library up and down in the library table. This does not affect the display order of libraries in the Symbol Editor or Symbol Chooser.

Libraries can be made inactive by unchecking the Active checkbox in the first column. Inactive libraries are still in the library table but do not appear in any library browsers and are not loaded from disk, which can reduce loading times.

A range of libraries can be selected by clicking the first library in the range and then Shift-clicking the last library in the range.

Each library must have a unique nickname: duplicate library nicknames are not allowed in the same table. However, nicknames can be duplicated between the global and project library tables. Libraries in the project table take precedence over libraries with the same name in the global table.

Library nicknames do not have to be related to the library filename or path. The colon character (:) cannot be used in library nicknames or symbol names because it is used as a separator between nicknames and symbols.

Each library entry must have a valid path. Paths can be defined as absolute, relative, or by path variable substitution.

The appropriate library format must be selected in order for the library to be properly read. The supported formats are listed above. Only KiCad format libraries (.kicad_sym) can be saved. Other symbol library formats are read-only and must be converted to KiCad format before you can modify them.

There is an optional description field to add a description of the library entry. The option field is not used at this time so adding options will have no effect when loading libraries.

The symbol library tables support path variable substitution, which allows you to define path variables containing custom paths to where your libraries are stored. Path variable substitution is supported by using the syntax ${PATH_VAR_NAME} in the symbol library path.

By default, KiCad defines several path variables which are described in the project manager documentation. Path variables can be configured in the Preferences → Configure Paths…​ dialog.

Using path variables in the symbol library tables allows libraries to be relocated without breaking the symbol library tables, so long as the path variables are updated when the library location changes.

${KIPRJMOD} is a special path variable that always expands to the absolute path of the current project directory. ${KIPRJMOD} allows libraries to be stored in the project folder without having to use an absolute path in the project library table. This makes it possible to relocate projects without breaking their project library tables.

Symbol libraries can be defined either globally or specifically to the currently loaded project. Symbol libraries defined in the user’s global table are always available and are stored in the sym-lib-table file in the user’s KiCad configuration folder. The project-specific symbol library table is active only for the currently open project file.

There are advantages and disadvantages to each method. Defining all libraries in the global table means they will always be available when needed. The disadvantage of this is that load time will increase.

Defining all symbol libraries on a project specific basis means that you only have the libraries required for the project which decreases symbol library load times. The disadvantage is that you always have to remember to add each symbol library that you need for every project.

One usage pattern would be to define commonly used libraries globally and the libraries only required for the project in the project specific library table. There is no restriction on how to define libraries.

Non-KiCad format libraries, including legacy libraries (.lib files), are read-only. They need to be converted to KiCad format (.kicad_sym files) before you can save changes to them.

Libraries in other formats can be converted to KiCad libraries by selecting them in the symbol library table and clicking the Migrate Libraries button. Multiple libraries can be selected and migrated at once by Ctrl-clicking or shift-clicking.

Libraries can also be converted one at a time by opening them in the Symbol Editor and saving them as a new library.

When loading a schematic created prior to the symbol library table implementation, KiCad will attempt to remap the symbol library links in the schematic to the appropriate library table symbols. The success of this process is dependent on several factors:

KiCad provides a symbol editing tool that allows you to create libraries; add, edit, delete, or transfer symbols between libraries; export symbols to files; and import symbols from files. The Symbol Editor can be launched from the KiCad Project Manager or from the Schematic Editor (Tools → Symbol Editor). You can also open the Symbol Editor from the a symbol in the schematic; in this way you can edit either the library copy or the schematic copy of that symbol in the editor.

In general, the flow for designing a symbol involves:

The Symbol Editor main window is shown below. It has three toolbars for quick access to common features and a symbol viewing/editing canvas. Not all commands are available on the toolbars, but all commands are available in the menus.

In addition to the toolbars, there are collapsible panels for the symbol tree, Properties Manager, and selection filter on the left. The bottom of the window contains a message panel that shows details about the selected object.

The button displays or hides the list of available libraries, which allows you to select an active library. When a new symbol is created, it will be placed in the active library.

Clicking on a symbol name opens that symbol in the editor, and hovering the cursor over the name of a symbol displays a preview of the symbol.

After modification, a symbol can be saved in the current library or a different library. To save the modified symbol in the current library, click the icon.

To save the symbol changes to a new symbol, click File → Save As…​. The symbol can be saved in the current library or a different library (including a new library), and a new name can be set for the symbol. Alternatively, you can use File → Save Copy As…​, which behaves the same as Save As except that the original symbol remains open rather than switching to the new symbol.

To create a new file containing only the current symbol, click File → Export → Symbol…​. This file will be a standard symbol library file which will contain only one symbol. The library will not be added to your library table.

The editor can also open symbols from the schematic. To edit a symbol from the schematic, right click a symbol in the Schematic Editor and select Open in Schematic Editor (Ctrl+E).

Editing and saving the schematic copy of a symbol will only update that symbol in the schematic; it will not update other copies of that symbol in the schematic, and it will not change the original library copy of the symbol. When you open the schematic copy of a symbol, the Schematic Editor displays an info bar that warns you the library copy will not be modified. You can click the link in this info bar to open the library version of the symbol instead, or press Ctrl+Shift+E.

You can create a new symbol library by clicking File → New Library…​. At this point you must choose whether the new library should be added to the global symbol library table or the project symbol library table. Libraries in the global library table will be available to all projects, while libraries in the project library table will only be available in the current project.

Following selection of the library table, you must choose a name and location for the new library. A new, empty library will be created at the specified location.

To create a new symbol in the current symbol library, click the button. You will be asked for a number of symbol properties.

There are also several graphical options.

These properties can also be changed later in the Symbol Properties window.

A new symbol will be created using the properties above and will appear in the editor as shown below.

The blue cross in the center is the symbol anchor, which specifies the symbol origin i.e. the coordinates (0, 0). The anchor can be repositioned by selecting the button and clicking on the new desired anchor position.

Symbol properties are set when the symbol is created but they can be modified at any point. To change the symbol properties, click on the button to show the Symbol Properties dialog. You can also double click an empty spot in the editing canvas.

It is important to set the number of units and check all units are interchangeable and has alternate body style, as applicable, because these settings affect how pins and graphics are added to each symbol unit.

If you change the number of units per package after adding the pins to the symbol, you will need to do extra work to add pins and graphics for the additional units. The pins and graphics would have been automatically added to each unit had these properties been correctly set initially. Nevertheless, it is possible to modify these properties at any time.

The graphic options Show pin number and Show pin name define the visibility of the pin number and pin name text. The option Place pin names inside defines the pin name position relative to the pin body. The pin names will be displayed inside the symbol outline if the option is checked. In this case the Pin Name Position Offset property defines the shift of the text away from the body end of the pin. A value from 0.02 to 0.05 inches is usually reasonable.

The example below shows a symbol with the Place pin name inside option unchecked. Notice the position of the names and pin numbers.

Symbols contain multiple fields, which are named values containing information related to the symbol. Fields can be displayed on the schematic or hidden and only shown in the symbol’s properties. Some fields have special meaning to KiCad: Reference and Footprint are both critical for creating a PCB, for example. Other fields may contain information that is important for a design but is not interpreted by KiCad, like pricing or stock information for a part.

Any fields defined in a library symbol will be included in the symbol when it is added to a schematic. You can also add new fields to symbols in the schematic. Whether they are in the library symbol or not, these fields can then be edited on a per-symbol basis in the schematic. They are also transferred to the symbol’s corresponding footprint in the PCB.

All library symbols are defined with five default fields: Reference, Value, Footprint, Datasheet, and Description, which are added whenever a symbol is created. These default fields cannot be deleted. Only the Reference field is required to have a value: the contents of a library symbol’s Reference field is used as the reference designator prefix when the symbol is added to a schematic. In the schematic, the symbol’s Reference field contains the entire reference designator.

The Footprint field, if used, contains a reference to a footprint for the symbol. The format is LIBNAME:FOOTPRINTNAME, where LIBNAME is the name of the footprint library in the footprint library table (see the Footprint Library Table section in the PCB Editor manual) and FOOTPRINTNAME is the name of the footprint in the library LIBNAME.

The Description field can contain text describing the symbol such as the component function, distinguishing features, and package options. Together with the symbol’s name and keywords, text in this field is used when searching for symbols in the Symbol Chooser or Symbol Editor. Before KiCad version 8.0, this was a dedicated property (like the symbol name and keywords) rather than a symbol field.

Symbols defined in libraries are typically defined with only these five default fields. Additional fields such as vendor, part number, unit cost, etc. can be added to library symbols but generally this is done in the schematic editor so the additional fields can be added to every symbol in the schematic, not just all symbols of one type.

To edit an existing symbol field, double-click the field, select it or hover and press E, or right-click on the field text and select Properties…​.

To add new fields, delete optional fields, or edit existing fields, use the icon on the main tool bar to open the Symbol Properties dialog. Fields can be arbitrarily named, but names starting with ki_, e.g. ki_description, are reserved by KiCad and should not be used for user fields.

Fields have a number of properties, each of which is shown as a column in the properties grid. Not all columns are shown by default; columns can be shown or hidden by right clicking on the grid header and selecting or deselecting columns from the menu.

The footprint filters tab is used to define which footprints are appropriate to use with the symbol. The filters can be applied in the Footprint Assignment tool so that only appropriate footprints are displayed for each symbol.

Multiple footprint filters can be defined. Footprints that match any of the filters will be displayed; if no filters are defined, then all footprints will be displayed.

Filters can use wildcards: * matches any number of characters, including zero, and ? matches zero or one characters. For example, SOIC-* would match the SOIC-8_3.9x4.9mm_P1.27mm footprint as well as any other footprint beginning with SOIC-. The filter SOT?23 matches SOT23 as well as SOT-23.

External files can be embedded within a symbol. Embedding a file stores a copy of the file inside the symbol. The symbol can then refer to the embedded copy of the file instead of the external file, which makes the symbol more portable as it doesn’t rely on an external file, although the symbol library’s filesize is increased as a result. In symbols this is especially useful for embedding datasheets and SPICE models. Files embedded in a symbol are deduplicated when the symbol is added to a schematic: if a file is embedded in a symbol, and multiple instances of that symbol are added to the schematic, only one copy of the file will be embedded, and all of the schematic instances will refer to the same embedded file. Files embedded in a schematic cannot be referred to in the parent schematic. File embedding is explained in more detail in the Schematic Setup documentation.

Symbols can have more than one unit per package, each with different graphics and pin configurations. This is often used for logic gates, opamps, or other components that have multiple subunits within one physical package. Symbols can also have up to two body styles, a standard symbol and an alternate symbol often referred to as a "De Morgan equivalent".

For example, consider a relay with two switches, which can be designed as a symbol with one body style and three different units: a coil, switch 1, and switch 2. Designing a symbol with multiple units per package and/or alternate body styles is very flexible. A pin or a body symbol item can be common to all units or specific to a given unit or they can be common to both symbolic representation so are specific to a given symbol representation.

By default, pins are specific to a unit and body style. When a pin is common to all units or all body styles, it only needs to be created once, no mattery how many units or body styles are used. This is also the case for the body style graphic shapes and text, which may be common to each unit, but typically are specific to each body style.

To add additional units to a symbol, set the Number of Units property to the appropriate number in the Symbol Properties dialog. By default, symbol units are named Unit A, Unit B, etc., but you can set an arbitrary name for the current unit using Edit → Set Unit Display Name…​.

Use the unit selection dropdown to select the unit you wish to edit.

To add an alternate body style, set the Has alternate body style (De Morgan) property in the Symbol Properties dialog.

If the symbol has an alternate body style defined, one body style must be selected for editing at a time. To edit the normal representation, click the icon. To edit the alternate representation, click on the icon.

Graphical elements create the visual representation of a symbol and contain no electrical connection information. You can draw new graphic shapes using the buttons on the right toolbar. The following types of objects are available:

Each graphic item (line, arc, circle, etc.) can be defined as common to all units and/or body styles or specific to a given unit and/or body style.

Element options can be quickly accessed by right-clicking on the element to display the context menu for the selected element. You can also double-left-click on an element to modify its properties, or edit its properties using the Properties Manager panel.

Below is the properties dialog for a polygon element.

Die Eigenschaften eines grafischen Elementes sind:

You can create and insert a pin by clicking on the button. Pin properties can be edited by double clicking on the pin. You can also delete or move pins that you have already added. Pins must be created carefully, because any error will have consequences on the PCB design.

A pin is defined by its graphical representation, its name, and its number. The pin’s name and number can contain letters, numbers, and symbols, but not spaces. For the Electrical Rules Check (ERC) tool to be useful, the pin’s electrical type (input, output, tri-state…​) must also be defined correctly. If this type is not defined properly, the schematic ERC check results may be invalid.

Wichtige Hinweise:

Power symbols are symbols that are used to label a wire as part of a global power net, like VCC or GND. The power symbol’s Value field determines the net label. The behavior of power symbols is described in the electrical connections section. Power symbols are handled and created the same way as normal symbols, but there are several additional considerations described below.

It may be useful to place power symbols in a dedicated library. KiCad’s symbol library places power symbols in the power library, and users may create libraries to store their own power symbols. If the Define as power symbol box is checked in a symbol’s properties, that symbol will appear in the Schematic Editor’s Add Power Symbol dialog for convenient access.

Power symbols consist of a single pin of type Power Input. They must also have the Define as power symbol property checked.

Below is an example of a GND power symbol.

Um ein Spannungsversorgungssymbol zu erstellen führen Sie folgende Schritte aus:

An easier method to create a new power symbol is to use another symbol as a starting point.

The Symbol Editor can check for common issues in your symbols. Run the symbol checker using the button in the top toolbar.

The symbol checker checks for:

Resistor, inductor, and capacitor models can be inferred, which means that KiCad will detect that they are passives and automatically assign an appropriate simulation model. Therefore they do not require any special settings; users only need to set the Value field of the symbol.

KiCad infers simulation models for symbols based on the following criteria:

Inferred models are ideal models. If the simulation requires a non-ideal model, for example an inductor with parasitic capacitance included, you must explicitly assign a model that includes it.

KiCad offers several standard simulation models. They do not require an external model file, and their parameters can be edited in KiCad’s Simulation Model Editor GUI. The following devices are available:

To add a built-in model to a symbol, open the Simulation Model Editor dialog (Symbol Properties → Simulation Model…​) and select Built-in SPICE model. You can then select the kind of device from the device dropdown and the device subtype from the device type dropdown.

Refer to the ngspice documentation for more details about these models and their parameters.

Device sets the type of device to simulate: a resistor, BJT, voltage source, etc. This value is stored in the symbol’s Sim.Device field.

Device type selects the type of model to use for the device. Most devices have several types of models to choose from. Models may vary in their degree of accuracy, which characteristics they are optimized for, what parameters they have available, and how many pins they have. For example, the ideal resistor type models a simple resistor with two terminals and a single resistance parameter, while the potentiometer resistor type models an adjustable resistor with three terminals and an additional parameter for wiper position. Some devices have an especially large number of types to choose from: N-channel MOSFETs, for example, have 17 available types, each of which uses a different mathematical model to simulate the transistor behavior. One model may be more or less appropriate than another for simulating a specific device or circuit or for performing a particular analysis. Refer to the ngspice documentation for detailed information about models and their parameters. The device type value is stored in the symbol’s Sim.Type field.

The parameters tab displays the parameters of the model and lets you edit them. For example, a resistor’s resistance, a voltage source’s waveform, a MOSFET’s width and length, etc. Any parameters that differ from the model’s defaults are stored in the symbol’s Sim.Params field.

The code tab displays the generated SPICE model as it will be written to the SPICE netlist for simulation.

The Save parameter '<parameter name>' in Value field checkbox uses the symbol’s Value field for storing parameters instead of the Sim.Params field. This may make it easier to edit simple models from the schematic, without opening the Simulation Model Editor. This option is only available for ideal passive models (R, L, C) and DC sources. If the field Sim.Params exists in the symbol, it will take priority over the Value field.

KiCad can also load SPICE models from external files, and this is typically how you will add a SPICE model of a specific commercially-available part (say, a 555 timer, or a TL071 operational amplifier, for example) to your simulation. These models must be in a standard SPICE format and must not be encrypted. Models such as these are readily available from numerous sources - manufacturer’s web-sites being just one example.

To load a model from an external file, open the Simulation Model Editor dialog (Symbol Properties → Simulation Model…​) and select SPICE model from file.

File is the path to the model file to use. Unencrypted model files are plain, human-readable text files and often have extensions such as .lib, .sub etc., although KiCad will accept a valid model with any extension.

The path to the file can be absolute, or relative to the project folder. The path can also be relative to the value of SPICE_LIB_DIR if you have defined that path variable. If you enable the Embed File checkbox in the file browser, the library file will be embedded in the schematic (or symbol library). This makes the schematic (or schematic) more portable as it doesn’t rely on an external library file. The library filename is saved in the symbol’s Sim.Library field.

Model is the name of the desired model in the model file. A model file may contain multiple models, and if so they will all be shown in the list. You can filter the list of models using the search box. The selected model is listed in the symbol’s Sim.Name field.

Parameters can be overridden (or additional parameters specified) using the Parameters tab. All parameters specified in the selected model or the Parameters tab are stored in the symbol’s Sim.Params field.

The Code tab displays the generated SPICE model as it will be written to the SPICE netlist for simulation.

IBIS (I/O Buffer Information Specification) files are an alternative to SPICE models for modeling the behavior of input/output buffers on digital parts. In order to load an IBIS file, users should follow the procedure for SPICE library models, but provide a .ibs file.

File is the path to the model file to use. The path can be absolute or relative to the project folder. The path can also be relative to the value of SPICE_LIB_DIR if you have defined that path variable. The library filename is saved in the symbol’s Sim.Library field. If an IBIS model file is loaded, the remaining fields in the dialog will relate to the IBIS model.

Component selects which component from the IBIS file to use, as IBIS files can contain multiple components. The component name is saved in the symbol’s Sim.Name field.

Pin selects which pin in the IBIS model to simulate. The selected pin must be mapped to a symbol pin in the Pin Assignments tab. The chosen pin’s number is saved in the symbol’s Sim.Ibis.Pin field.

Model is the list of models available for the selected pin, for example an input or an output. The chosen model name is saved in the symbol’s Sim.Ibis.Model field.

Type selects what the pin should do in the simulation. A pin can be a passive device that doesn’t drive any value; it can be a DC driver that drives high, low, or high-impedance; or it can be a rectangular wave or PRBS driver. This value is stored in the symbol’s Sim.Type field.

The Parameters tab lets you see and edit the parameters of the model. For each parameter, you can switch between a minimum, typical, or maximum value, as defined in the IBIS file. You can also choose the parameters of the driven waveform, depending on the pin’s chosen type. Any parameters that differ from the defaults are stored in the symbol’s Sim.Params field.

Simulation models may have their pins numbered differently than the corresponding symbol. For example, SPICE models for diodes usually consider pin 1 to be the anode, while schematic symbols are usually drawn with pin 1 as the cathode. Operational amplifier models are also very likely to have model pin assignments that do not match package or schematic pin numbers.

You can use the Simulation Model Editor’s Pin Assignments tab to map the symbol’s pins to the simulation model pins.

The left column displays the name and number of each symbol pin, i.e. the pin numbers and names that appear on the schematic part in KiCad. The right column displays the corresponding pin as defined in the model file in use. For each symbol pin, you can select the corresponding pin from the simulation model in the dropdown in the right column. In the cases where a schematic part has pins that are not in the model, as in the case of an operational amplifier with 'nulling' pins that are not modeled, the schematic part pin may be assigned to the 'Not Connected' option in the Pin Assignments dropdown. Unlike other pin assignments, 'Not Connected' may be assigned to multiple pins if necessary.

When you use a subcircuit model, the dialog displays the model’s code under the pin assignments for use as a reference while assigning pins. A well-written model will often include a helpful reference section (as a set of comments) to inform the user how the model pins are mapped.

To run a simulation, open the SPICE simulator dialog by clicking Inspect → Simulator in the schematics editor window or using the button in the top toolbar.

The dialog is divided into several sections:

Workbooks are files that store information about the simulation environment, including simulation setup parameters and the list of signals available for use. They can be used to store the setup for a set of analyses, which can then be reloaded and rerun at a later time. A workbook can include more than one simulation - for example, it may contain separate tabs for Transient (TRAN), Operating Point (OP), and Small Signal AC (AC) analyses which you added as you worked.

You can save a workbook using File → Save Workbook and load one using File → Open Workbook.

Before running a simulation, you need to select a simulation type and set the simulation parameters. This can be done using Simulation → Settings…​ or the Sim Command button () and then selecting one of the available analysis types:

These analysis types are explained in detail in the ngspice documentation.

Another way to configure a simulation is to type SPICE directives into text fields on schematics. Any text field directives related to a simulation command are overridden by the settings selected in the dialog. This means that once a simulation has run, the dialog overrides the schematic directives until the simulator is reopened.

Once the simulation command is set, a simulation can be started with Simulation → Start Simulation (Ctrl+R) or the Run/Stop Simulation button ().

It is possible to adjust the value of basic components in the schematic from within the simulation interface, which lets you conveniently adjust component values based on simulation results. Each time the component value is tuned, the simulation is re-run with the new component value. You can tune the value of passive resistors, inductors, and capacitors, or the voltage or current of DC voltage and current sources.

To tune a component, use Simulation → Add Tuned Value…​, the keyboard shortcut T, or the button in the toolbar, and then click on the component to tune in the schematic. This adds a tuning control for that component in the bottom right corner of the simulator window. Multiple components can be tuned at once, with a separate tuning control per component.

In addition, it is possible to restrict the component values to those from a particular series of Preferred Values — either of the E24, E48, E96 or E192 series. This is particularly useful when it is necessary to restrict component values to commercially available parts.

KiCad’s simulator offers two ways to export results:

Only simulations that produce plots (see above) can be exported as an image or a CSV file. The results of OP and PZ analyses cannot be exported in this way.

Sometimes a simulation will fail, either with or without errors being reported. Paying attention to the error messages reported, taking care in the development and entry into KiCad of the circuit to be simulated, and making use of the KiCad, ngspice and general SPICE documentation and information from fellow users in forums is very worthwhile and can often point the way to a solution.

It’s worth noting, for users unfamiliar with SPICE, ngspice or circuit simulation in general that some 'common' and interesting circuits can sometimes be tricky to simulate accurately or reliably. These include apparently simple circuits such as oscillators, which in some cases may fail to oscillate at all! It is nearly always possible to build a working simulation but sometimes this can more require SPICE experience than might be initially apparent, or the guidance of someone who already has it. The ngspice documentation, once again, is worth reading for insights into good and effective simulation practices if you are encountering difficulty.

Fundamentally the KiCad Simulator is a user-friendly front-end to the powerful ngspice circuit simulator. Therefore problems with the details of simulation, the correct use of SPICE elements, models, etc. is beyond the scope of the KiCad documentation but is very likely to be fully and completely addressed in the ngspice documentation itself. It’s therefore recommended not to overlook this valuable resource.

Although it is certainly possible to keep simulation models (i.e. .lib, .sub files) in the directories associated with individual KiCad projects, this will likely result in unnecessary copies of model files proliferating as you create simulations. Consider creating a dedicated storage location (directory, folder) for models, perhaps organized by manufacturer or device type, to hold these files. Then they may simply be referenced in simulations at a common location.