AutoCAD 2021 has introduced some enhancements to the External Reference (Xref) command.   Previously in AutoCAD when an Xref changed the software would prompt that the drawing would need to be updated.  (see below image) and that was it.  It updated you saw more geometry being introduced to your drawing and you would carry on.

The Xref enhancement introduces some more information on what has changed.  Firstly you will note that the “External Reference File has Changed” popup has been renamed to “An Xref was modified” popup.   A tick box has been added to compare your changes. Now what exactly is this?

Selecting Reload xref 2 – by aldred gives the following.

Selecting the settings button on the left allows you to customise the colours that AutoCAD will use for the different comparisons in your updated xref.

• Not in Current Xref – this has been removed/deleted from the xref
• Only in Current Xref – this has been added to the Xref
• No Differences – has not been deleted or added to the Xref
• Not Compared – not partaking in the comparison

A revision cloud is also drawn around the objects that have been either added or deleted.

In all the above settings if you select the lightbulb it turns the preview of the object on or off.  Selecting the colour square opens the colour palette which allows the user to select their own colours for the AutoCAD comparison.

If hatch or text was added to the xref then you can turn the visibility of that on or off in the comparison.

Once the colours have been set then you can navigate through the changes by selecting the arrows present on the comparison bar.  When you are ready to move on from the comparison select the green tick.

Once again Autodesk bringing some welcome enhancements to AutoCAD.