Altium Designer Documentation

Working with a Compile Mask Object on a Schematic Sheet in Altium Designer

Created: July 27, 2015 | Updated: July 20, 2020
Now reading version 17.1. For the latest, read: Compile Mask for version 21
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Parent page: Schematic Objects

A placed Compile Mask, hover to collapse.


A compile mask is a design directive. It is used to effectively hide the area of the design it contains from the Compiler, allowing you to manually prevent error checking for circuitry that may not yet be complete and you know will generated compile errors. This can prove very useful if you need to compile the active document or project to check the integrity of the design in other specific areas, but do not want the clutter of compiler-generated messages associated with unfinished portions of the design.


Compile masks are available for placement in the Schematic Editor only, by choosing the Place » Directives » Compile Mask command, from the main menus.


After launching the command, the cursor will change to a cross-hair and you will enter compile mask placement mode. Placement is made by performing the following sequence of actions:

  1. Position the cursor and click or press Enter to anchor the first corner of the mask.
  2. Move the cursor to adjust the size of the mask, such that it completely encapsulates the area of the design that you want hidden from the Compiler, then click or press Enter to anchor the diagonally-opposite corner and thereby complete placement of the mask. Design objects falling completely within the bounds of the mask will become grayed-out.
  3. Continue placing further compile masks, or right-click or press Esc to exit placement mode.
Press the Tab key during placement to access an associated properties dialog, from where properties for the compile mask can be changed on-the-fly.

While attributes can be modified during placement (Tab to bring up associated properties dialog), bear in mind that these will become the default settings for further placement unless the Permanent option on the Schematic – Default Primitives page of the Preferences dialog is enabled. When this option is enabled, changes made will affect only the object being placed and subsequent objects placed during the same placement session.

Graphical Editing

This method of editing allows you to select a placed compile mask object directly in the workspace and change its size, shape or location, graphically.

A compile mask can be displayed in either expanded (full frame) or collapsed (small triangle) modes. These modes correspond to the mask being enabled and disabled respectively. Toggle the display mode by clicking on the top-left corner of a placed compile mask.

Click the triangle in the top-left corner to collapse (and disable) a compile mask.

When a fully expanded compile mask object is selected, the following editing handles are available:

A selected Compile Mask (fully expanded).

  • Click and drag A to resize the compile mask in the vertical and horizontal directions simultaneously.
  • Click and drag B to resize the compile mask in the vertical and horizontal directions separately.
  • Click anywhere on the compile mask – away from editing handles – and drag to reposition it. While dragging, the compile mask can be rotated (Spacebar/Shift+Spacebar) or mirrored (X or Y keys to mirror along the X-axis or Y-axis respectively).

The size and shape of a compile mask cannot be changed graphically when it is in collapsed mode, only its location/orientation. As such, editing handles are not available when a collapsed compile mask object is selected:

A selected Compile Mask (collapsed).

  • Click anywhere inside the dashed box and drag to reposition the compile mask as required. The compile mask can be rotated or mirrored while dragging.

If attempting to graphically modify an object that has its Locked property enabled, a dialog will appear asking for confirmation to proceed with the edit. If the Protect Locked Objects option is enabled on the Schematic – Graphical Editing page of the Preferences dialog, and the Locked option for that design object is enabled as well, then that object cannot be selected or graphically edited. Double click on the locked object directly and disable the Locked property or disable the Protect Locked Objects option, to graphically edit the object.

Non-Graphical Editing

The following methods of non-graphical editing are available:

Via an Associated Properties Dialog

Dialog page: Compile Mask

This method of editing uses the following dialog to modify the properties of a compile mask object.

The Compile Mask dialog.

The Compile Mask dialog can be accessed prior to entering placement mode, from the Schematic – Default Primitives page of the Preferences dialog. This allows the default properties for the compile mask object to be changed, which will be applied when placing subsequent compile masks.

During placement, the dialog can be accessed by pressing the Tab key.

After placement, the dialog can be accessed in one of the following ways:

  • Double-clicking on the placed compile mask object.
  • Placing the cursor over the compile mask object, right-clicking and choosing Properties from the context menu.
  • Using the Edit » Change command and clicking once over the placed compile mask object.

Via the SCH Inspector Panel

Panel pages: SCH Inspector, SCH Filter

The SCH Inspector panel enables the designer to interrogate and edit the properties of one or more design objects in the active document. Used in conjunction with appropriate filtering - by using the SCH Filter panel, or the Find Similar Objects dialog - the panel can be used to make changes to multiple objects of the same kind, from one convenient location.

Via the SCH List Panel

Panel pages: SCH List, SCH Filter

The SCH List panel allows the designer to display design objects from one or more documents in tabular format, enabling quick inspection and modification of object attributes. Used in conjunction with appropriate filtering - by using the SCH Filter panel, or the Find Similar Objects dialog - it enables the display of just those objects falling under the scope of the active filter – allowing the designer to target and edit multiple design objects with greater accuracy and efficiency.


  1. While compile masks can be rotated or mirrored along the X or Y axis, this has no effect on the orientation of the design circuitry within.


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