Fonts developed by the Adobe Type team are intended to be broadly usable across as many operating systems as possible. This means loads and loads of testing, much of which happens with specialized testing tools built in-house.

One of those tools is the Annotated OpenType Specification (AOTS), which Eric Muller developed during his tenure on the Core Type team at Adobe. Team members have used AOTS at Adobe to test and fix shaping engines, which are essential for (among other uses) properly displaying the alternate glyphs associated with ligatures and OpenType features.

We have now made this software open source, and you can find it on the public Adobe Type Tools GitHub repository. For anyone who develops text engines, this is a valuable tool as it provides an extensive low-level test suite. And anyone working with font files can use the decompiler/compiler to closely inspect and modify fonts.

Eric has since moved on to another company, but he is still using the software in his work — most notably to improve Harfbuzz, an open source text engine and shaper. We’re excited to make the software freely available as open-source, because ultimately it means better text and font handling for an even broader audience.

Check out the AOTS GitHub repository for more details. If you have any questions or feedback, please open a new issue or join a relevant open issue thread.