Many people have asked me about a Diff tool for Open XML: something that would show what has changed in an Open XML document, so that you can compare two versions of a document and easily see the differences.
A diff tool for Open XML is not a trivial thing to build, because there are various types of parts which may change, and relationships between those parts may change, content types may change, you may have non-XML parts, and ... lots of details.
Stephane Rodriguez has decided to work through those details, and the result is a very useful utility for Open XML developers and users: DIFFOPC, a diff tool for OPC (Open Packaging Convention) packages such as Open XML documents and XPS (XML Paper Specification) documents.
You can download Stephane's diff tool here, and he also has provided some information about how to use it.
I've tried this tool on Windows Server 2003, XP, and Vista, and it works great. There's color-coding to show whether parts have been added, deleted, or changed, and you can click on a specific part to see the differences between the two versions of that part as well. The diff reports are all rendered as simple HTML, so you can save them or search them easily as needed.
It's great to see these kinds of tools starting to appear for Open XML developers. Thanks, Stephane!