Development releases for the L3 Programming Layer (aka expl3)

The team have made development releases of the LaTeX kernel available for some time, to allow active users and developers to test new features. We have now extended this concept to cover the core of expl3 (packages l3kernel and l3backend) that is automatically loaded by the LaTeX kernel as the ‘L3 Programming layer’. The new CTAN packages l3kernel-dev and l3backend-dev will be used when building the development LaTeX formats, allowing testing of changes to expl3 before its release and thus before it becomes active in the production version of LaTeX.

We encourage interested users, and especially developers, to try out the development formats, which will now include testing a pre-release of the L3 Programming Layer expl3.

Unlike the LaTeX kernel, expl3 does not have a fixed release schedule. To allow for that, the aim is that there will be an l3kernel-dev upload to CTAN around two weeks before the upload of the ‘production’ version. This should be enough time for testing but still allow a quick turn-around as features are added to expl3.

— Joseph & Frank