The Open XML SDK is Now Open Source

Today MS Open Tech has announced the release of the Open XML SDK version 2.5 as open source software (Apache 2.0 license) under the stewardship of the .NET Foundation.  Brian Jones, who was instrumental in the creation of the Open XML standard, as well one of the folks behind the Open XML SDK, provides some historical background on Open XML, and the significance of this release.

I’ve been happy to announce the release of various other open source projects, but I’ve rarely been as delighted and enthusiastic as I am about this news.  This opens up a new era of power and flexibility for Open XML developers.  Open source developers can address bugs and build enhancements to the SDK in ways that were not available to us previously.

Because the SDK is licensed under the Apache 2.0 license, there are no platform restrictions.  I personally plan to port the SDK to other platforms such as Linux and OSX using the Mono C# compiler and the MONO .NET development framework.  I’ll start on these ports as time and schedules permit.

The Open XML SDK is hosted by GitHub at

For download and installation instructions, see Open XML Installation Center

This is the source code for the official binary of version 2.5 of the SDK.  There are no enhancements or bug fixes to this release.  Version 2.5 was a super-high quality release, and we feel that there is value in releasing the version 2.5 source code without modifications.  We can then use this as a starting point for making some interesting enhancements, as well as addressing a couple of bugs that inhibit development for some developers.  If you don’t need the source code, you can continue to use the released binary of the Open XML SDK v 2.5.

This release does not include the code for the Open XML SDK Productivity Tool.  However, since the productivity tool fully supports v 2.5, you can continue to use the existing installable tool seamlessly.  If you use the document reflector to generate code, you can compile that code using the open source version of the Open XML SDK.

In addition to open sourcing of the SDK, Microsoft has also opened all of the Open XML conceptual documentation in MSDN for public review / contributions.  A copy of the documentation is now in Github for you to edit and review.

Going forward, a key goal will be to maintain perfect backwards compatibility.  As we fix bugs and enhance the SDK, we want to make sure that existing programs written using previous versions of the SDK continue to work.  We plan on introducing no breaking changes.

That said, I have some interesting ideas about ways to enhance the SDK, and if you have ideas as well please get involved and contribute to the project.  Stay tuned to this blog here on, where  I’ll be aggregating all news about the Open XML SDK.