Microsoft open sources Infocom’s Zork trilogy

Microsoft, in conjunction with Activision, Team Xbox, and its Open Source Programs Office, has announced plans to open source some of Infocom’s most iconic interactive fiction. Zork I, Zork II, and Zork III will be released under the MIT License, placing the code for one of the most recognisable early computer game series into accessible public repositories. As someone who spent many hours playing the Zork trilogy (and other Infocom games) over the years, this is fantastic news.

Developers, students, and researchers will be able to examine the structure of the original titles directly rather than relying on secondary documentation or archived binaries. It will also provide a clearer view of how Infocom’s early work was built, maintained, and adapted across platforms.

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Zork began on a mainframe at MIT in the late 1970s before Infocom adapted it for consumer computers. The original version was too large for early home systems, so Infocom split the project into three parts and used the Z-Machine, a virtual machine created to run the same code across different platforms. This approach let the trilogy appear on systems ranging from the Apple II to the IBM PC without rewriting the core codebase.

For the open-source release, Microsoft has worked with Jason Scott of the Internet Archive to submit upstream pull requests to the historical Zork repositories. These pull requests add the MIT License and formally document the open-source grant. The repositories contain the source code and any surviving materials such as comments, notes, and files that reflect the development process.

The release focuses entirely on code. It does not include commercial assets such as artwork, branding, packaging, or any other materials tied to the retail versions of the games. The intention is to preserve the technical record and make it available for examination rather than recreate a full commercial distribution.

Play Zork

Zork remains available commercially through The Zork Anthology on Good Old Games (GOG), but anyone who wants to compile the original code can use ZILF, a modern toolchain created by Tara McGrew.

ZILF compiles ZIL source files into Z3 format, which can then be run using interpreters such as ZLR or Windows Frotz. This continues a long tradition of community-maintained tools built to support Z-Machine titles.

Microsoft says that once the pull requests are merged, the historical repositories will remain the permanent home for the code. Contributions will be welcome as long as they are limited in scope, documented clearly, and do not alter the character of the original work. The purpose of open sourcing the code is to support education and preservation, not to update the games or introduce new features.

Zork occupies an important place in the history of interactive fiction and early game design. Making the code open source gives the wider community direct access to the techniques and structures that defined one of the most influential text adventures of all time. You can find out more about the plans here.

What do you think about Microsoft making Zork open source? Let us know in the comments.