Design Data Comparisons

Updated: August 11, 2026

The Altium 365 Workspace project view provides design data comparison features that allow you to compare data changes that have occurred between different project releases and/or commits. Particularly valuable for performing final checks prior to sending your product data to the manufacturing side, the features allow you to determine exactly what changes have occurred in your Gerber (or ODB++), Schematic. PCB, and BOM data between release/commit events.

Fabrication Comparison

Making a final check of your fabricated board data prior to sending out to the manufacturer is always a good thing. The Gerber and ODB++ comparison features facilitate just that, with the ability to quickly check to ensure no differences in your fabrication output between released iterations of your design project. It provides a purely graphical, layer-by-layer comparison, highlighting areas with changes using a bounding box and a number.

Fabrication Comparison Access

The Gerber and ODB++ comparison features can be accessed from the Workspace design History, Releases and Manufacturing Portal views. The below example outlines the Gerber file comparison feature which applies equally to the ODB++ comparison functionality - this is accessed from the ODB++ to menu option.

In the project's History view, click the control at the top-right of a Project Released event tile and select the Gerber to option from the drop-down menu. Then choose to compare against the previous release's fabrication data, select from all possible releases, or compare against a local file set (see below).

in the project's Releases view, click the button associated with a specific release of that project and choose the Gerber to option from the drop-down menu. Then select which other release's fabrication data to compare against, or a local file set to compare against (see below).

In the Manufacturing Portal browser view when viewing a specific release package for a design project, click the button at the top-right of the page and choose the Gerber to option. Then select which other release's fabrication data to compare against, or compare against a local file set (see below).

Comparing with a File Set

You also have the ability to compare the Gerber'ODB++ data in a release package against another Gerber/ODB++ file set available in the Workspace. This enables you to compare against, for example, Gerber/ODB++ data that has been generated locally from the latest live design, prior to making the next formal release of the project to your Workspace.

As noted in the above Access section (for Gerber), this comparison is performed by choosing the Gerber to » Files entry in the applicable menu. In the Select Fabrication or Release for Comparison window that follows, navigate to and select a Gerber file set to compare against. When confirmed () the comparison engine will process the differences and display the results in the interactive Gerber Compare view. Note that an available Release package also can be selected for comparison.

In terms of CAM manufacturing files, you can upload a full set of Gerber files plus NC Drill data (within a Zip archive). Ensure that there is only a single listing (or folder) of Gerbers inside the archive. Ensure that the drill files are in the same listing (or folder) as the Gerber files. If located in a separate folder, they will be ignored.

The Gerber Comparison feature supports the comparison of data in a release package against a locally generated file set.

Gerber/ODB++ Comparison Result

Once the comparison release or local file set has been chosen, the results of the comparison are presented in the Compare view, which opens in a separate browser tab. Again, the example shown were applies to both a Gerber and ODB++ comparison. Example ODB++ file comparison:

Depending on the number of differences that exist, it can take a while to generate the comparison data. You can either wait, or close the Compare view – an email will be sent to you once the data is ready to view. Click the button in the email to access the Compare view again.

The generated comparison is initially presented in a split view (Side by Side) showing the differences between the two Gerber or ODB++ sets. Color coding is used to distinguish the older data (Red) from the newer data (Green). View adjustments such as pan, zoom and net selections are synchronized between the two sides.

Select the Combined option to view both color-coded data sets overlaid in a single board view. In both the combined and split views each detected difference is numbered and outlined for the currently selected layer – these correspond to the annotated entries in the Layers pane on the left.

Select a layer difference entry in the Layers pane to highlight the related PCB area in the Gerber view, which will automatically pan and zoom to the location.

A selected difference is similarly shown in the Side by Side (split) view. Click on another layer entry in the Layers pane to view and select the annotated differences on that layer.

Browsing Controls

Browsing controls for the main viewing area are as follows:

Mouse wheel forward/backward to zoom in/out.
Click & hold (or right-click & hold), then drag to pan the document.

Taking Measurements

You can freely measure between any two points within the view, without any snapping guidance whatsoever. To do so, click the button. The Measurements pane opens, the cursor changes to a cross-hair, and you will enter measurement mode.

Measurement is performed as follows:

Position the cursor to where you wish to start measuring (Point 1) and click. The point is marked using a small white cross.
Move the cursor to the required end point (Point 2) and click again. As you move the cursor, a measuring line is displayed as an aide, showing the current XY distance (from Point 1 to the end of the line).

Right-click before defining Point 2 to start afresh – ready to define Point 1 again.

The Measurements pane reports the XY distance measured, the X (horizontal) distance, and the Y (vertical) distance.

Measurement units will initially be those used for the design itself, but can be switched between metric (mm) and imperial (mil) from the Info pane of the interface (accessed by clicking

in the top-right control cluster).

Continue measuring the distance between other points, or click the button again (or Esc) to exit measurement mode.

Example measurement taken on the Compare view of the Gerber data.

The last five measurements are listed in the Previous Measurements region of the Measurements pane. The most recent is at the top of the list. Click on an entry to retrieve that measurement – both in the pane and graphically in the main viewing area.

Measurements are available during the current session of the web page only. If you refresh the browser tab, the previous measurements will be cleared.

Schematic Comparison

Along with the comparison of Gerber data (see above), the project view also provides the ability to compare project schematic documents in a simple interactive interface. This offers a quick and convenient way to see only what changes have occurred between schematic iterations.

The Schematic Comparison feature presents differences graphically and as parametric data, which are listed in an associated Compare pane that allows cross-probing to the related schematic object(s). A comparison can be invoked between project Releases, project Commits, or between project Commits and Releases (available from the History view).

Schematic Comparison Access

The Schematic comparison feature can be accessed by:

Choosing the Schematic to option from the button menu in the Releases view, and then which other release's design source data to compare against. Or by choosing the same option in the Manufacturing Portal browser tab when viewing a specific project release package, and then which other release's source data to compare against.

Open the Schematic Compare feature from the ellipsis menu in the Releases or Manufacturing Portal view.

Open the Schematic Compare feature from the ellipsis menu in the Releases or Manufacturing Portal view.

Choosing the Schematic to option from the control at the top-right of a Commit or Release event tile in the History view, and then another Commit/Release event to compare against. Schematic data from the last release/commit can be selected (Previous Release or Previous Commit), or the data from any Commit/Release event by choosing the Select Commit or Release option – select the target comparison event by clicking on its tile.

Open Schematic Compare from the History view in Altium Designer or the Altium 365 browser interface.

Both the Gerber Compare and Schematic Compare features can be accessed from the equivalent History view in Altium Designer, when connected to an Altium 365 Workspace.

Schematic Comparison Result

When the comparison Commit/Release pair has been selected, the results of that comparison are opened as the Schematic differences view in a new browser tab. The first schematic in the source documents is presented by default, and the logical differences found (changed Components and Nets data) for all schematics are presented as a selectable list in the Compare pane on the left. Note that purely graphical changes, such as a moved component, are not included at this time.

Depending on the number of differences that exist, it can take a while to generate the comparison data. You can either wait, or close the Schematic Compare view – an email will be sent to you once the data is ready to view. Click the button in the email to access the Schematic Compare view again.

Select an item in the Compare list to cross-probe to its symbol in the associated schematic document.

The related component item is highlighted and its details shown in the Info pane on the right. Note that any parameter changes are highlighted in red.

Hover the cursor over the comparison data names at the top of the window to see the name of the user who created each Commit/Release, and any attached notes.
You can open and view the Commit/Release of either comparison source from their name entries in the top margin.

Select a listed element in the Compare pane to expose any available change details and cross-probe to its schematic graphic. Each element in the list has an associated icon indicating its general change status – red: removed, green: added, yellow/orange: modified. The same coding is used in the cross-probed schematic graphics.

The pane's differences list is grouped by Components and Nets:

Components – Each entry includes a summary of the change and the names of affected components. Select the designator (RefDes) of a component included in the entry (highlighted in blue) to cross-probe to its schematic graphic.
Nets – Each entry includes a summary of the change and the name of the affected net. Select a Net entry in the pane to cross-probe to the entire net on the active schematic, or expand the list to see and select the specific modification that affected the net.

Use the pane's listing Filter () to constrain the entries by a specified object or difference type.
Use the pane's listing Search () to locate entries by a typed search string.

Select a Component entry in the Compare pane to cross-probe to its highlighted graphic representation in the schematic document.

Select a Net entry in the Compare pane to cross-probe to its highlighted graphic representation in the schematic document.

Select a specific net modification in the expanded Net entry, such as the addition or removal of a component pin, to cross-probe to its highlighted graphic representation in the schematic document.

A icon associated with a Net entry in the Compare pane indicates the presence of that net in other schematic documents. Select the icon to access a drop-down list of those schematic documents, where the document affected by the currently selected net change is indicated by a yellow dot. Choose a schematic document from the menu to cross-probe to the net on that schematic, which is highlighted accordingly.

The entry for a modified Net includes a link to other schematic documents that also include the Net.

PCB Comparison

As a companion to Schematic compare, the Workspace project view offers a PCB comparison feature that detects and shows changes to the board design that have occurred between project commits and/or release iterations.

The PCB Compare feature provides a highly visual, Interactive interface for viewing PCB layout differences and the associated comparison data, with reactive cross-probing available between listed data differences and their associated graphics elements. A PCB comparison can be invoked between project Releases, project Commits, or between project Commits and Releases (available from the History view).

PCB Comparison Access

The PCB comparison feature can be accessed by:

Choosing the PCB to option from a release entry's button menu in the Releases view, and then which other release's design source data to compare against. Or by choosing the same option in the Manufacturing Portal when viewing a specific project release package, and then which other release's source data to compare against.

Choosing the PCB to option from the control at the top-right of a Commit or Release event tile in the History view, and then another Commit/Release event to compare against. Schematic data from the last release/commit can be selected (Previous Release or Previous Commit), or the data from any Commit/Release event by choosing the Select Commit or Release option – select the target comparison event by clicking on its tile.

When invoked, the Altium 365 platform's PCB comparison engine processes data differences between the selected PCB designs, which may take some time with more complex PCB designs. If the analysis time exceeds a predefined threshold, a notification email will be sent to your registered email address when the PCB comparison has completed. Note that the comparison data is cached, so a subsequent comparison of the same data incurs a minimal processing delay.

PCB Comparison Result

When the comparison Commit/Release pair has been selected, the results of that comparison are opened as the PCB Changes view in a new browser tab. The view presents the PCB compare engine results as a graphical representation of the board with unchanged elements shown in monochrome, and modified net-connected elements highlighted in green (added), red (removed) and yellow (modified). Note that modified Polygons are dimmed to enhance the clarity of board Net elements.

The Differences pane on the left lists the detected differences within groups of object types – Components, Nets, etc. When a difference entry is selected in the pane it expands to list the sub-elements that make up that detected difference, while the board view will automatically pan and zoom to show the area of change.

The initial PCB Compare view will highlight all detected differences. The changed elements are color-coded by their added, removed, or modified status.

Select an entry to expand its sub-elements and zoom/highlight the difference in the PCB view. The change details are shown in the Info pane on the right. Click again to deselect the entry and restore the default overview.

Here, a modified Net entry is selected. Note that the previous data, including the PCB net path and net length information, are shown in red – the current (updated) net path is green.

The below example shows how the location and associated routing for component R13 has changed between subsequent Commits/Release events, and how that difference is presented in the corresponding PCB Compare view. The differences, as listed in the PCB Compare pane, include modification entries for R13 and its two associated Nets (NetC9_1 and NetJ1_7).

Added net-based elements are shown in green, removed elements in red, and modified elements in yellow.

The differences can be examined in more detail by selecting individual change elements within the expanded sub-list under each difference entry. When selected, the parameter and positional changes are visually highlighted in the board view as red and green, and Net entries also will include calculated changes to the overall Routed Length.

You can open and view the Commit/Release of either comparison source from their name entries in the top margin.

Controlling Layer Visibility

The assessment of PCB Comparison differences can be enhanced by decluttering the view by reducing the number of visible Layers, particularly with complex high-density board layouts. This is performed through the Layers pane, opened from the control above the board view. The control's numeric text will dynamically change to indicate the current number of enabled layers compared to the total available layers.

Use the icon associated with each layer entry to toggle its visibility in the board view. The pane's layer entries are grouped in functional categories (Copper, Solder Mask, etc), where the visibility of each complete category can be toggled with its associated icon. Re-enable the visibility of all layers using the icon at the top.

Toggle the visibility of individual layers or collected groups of layers.

Similarly, use the pane's Only option associated with each layer and layer group to enable viewing of only that layer/group (all others are disabled). Re-enable the visibility of all layers using the icon at the top. Use the Top View and Bottom View options to flip the board view, while maintaining the current layer and differences selections.

Select the individual view of any layer – effectively single layer mode – or flip the view between the Top and Bottom board views.

BOM Comparison

The project view also provides a quick BOM Comparison feature to detect and show any design component data changes that have occurred between commit and/or release iterations. The differences are reported in text (CSV) form and made available as a local download.

The BOM Compare feature requires that the Commit or Release events being compared include an ActiveBOM document.
BOM comparisons also can be made between Managed BOM files and Releases in the BOM Portal application. See Managed BOM Compare.

BOM Comparison Access

The BOM Comparison feature can be accessed by:

Choosing the BOM to option from the button menu in the Releases view, and then which other release's data to compare against. Or by choosing the same option in the Manufacturing Portal browser tab when viewing a specific project release package, and then which other release's data to compare against.

Open the BOM Compare feature from the ellipsis menu in the Releases or Manufacturing Portal view.

Open the BOM Compare feature from the ellipsis menu in the Releases or Manufacturing Portal view.

Choosing the BOM to option from the control at the top-right of a Release or Commit event tile in the History view, and then another Commit/Release event to compare against. BOM data from the previous Commit or Release can be selected (Previous <Commit/Release>), or the data from any Commit/Release event by choosing the Select Commit or Release option – select the target comparison event by clicking on its tile.

Open Schematic Compare from the History view in Altium Designer or the Altium 365 browser interface.

BOM Comparison Result

The system will compare the BOM data between the specified project Releases or Commits, and then open the results of that comparison as the BOM differences view in a new browser tab. This view is populated with a list of color-coded entries that represent BOM items that have changed between the specified BOM events. Additional information and control is provided by the BOM Compare pane on the left, which allows you to choose an alternative design Variant, navigate the change entries, and apply Filters () to select/deselect the inclusion of component change categories (Added, Removed, Modified, etc).

The initial BOM Compare view includes entries representing the differences between the source and target BOM documents.

The BOM Comparison interface offered a range of features for accessing differences information. These include:

Hover the cursor over the icon associated with a BOM compare entry to see a summary of the changes that have occurred.

Use the Column Settings menu () to enable or disable the inclusion of specific component parameter data columns.

You can switch between and view the two BOM documents being compared using the view's upper data source tabs. A selected BOM entry line is maintained in all views (if available), which allows a difference selected in the Compare view to be quickly located in the two source BOM documents.

The BOM Compare view with the Compare tab active and a particular BOM difference entry selected.

The compare view with the source BOM document selected. The focused component is shown in the listing.

The component is not shown in the target BOM document since it has been removed from the PCB design.

Hover the cursor over the comparison data names at the top of the window to see the name of the user who created each Commit/Release, and any attached notes. You can open and view the Commit/Release of either comparison source from their name entries.

Invoked from the download option (), the comparison engine will also generate a summary of any updates in a standard CSV format. The BOM comparison summary is generated for the currently selected Variant of the design, and includes details of BOM data that has changed – been updated – between the specified project releases/commits.

The downloaded BOM comparison CSV files show data that has been updated between the project releases specified when invoking the compare feature.

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