The repository contains development material for expl3. This includes not only code to be developed into the expl3 kernel, but also a variety of test, documentation and more experimental material. All of this code works on top of LaTeX2e.

The following directories are present in the repository:

• l3kernel: code forms the expl3 kernel and all stable code. With a modern LaTeX2e kernel, this code is loaded during format creation; when using an older LaTeX2e kernel, this material is accessible using the expl3 package.
• l3backend: code for backend (driver) level interfaces across the expl3 codebase; none of this code has public interfaces, and so no distinction is made between stable and experimental code.
• l3packages: code which is written to be used on top of LaTeX2e to explore interfaces; this bundle is now made up of historical material, and the concepts have been migrated to the LaTeX2e kernel
• l3experimental: code which is written to be used on top of LaTeX2e to experiment with code and interface concepts. The interfaces for these packages are still under active discussion. Parts of this code may eventually be migrated to l3kernel.
• l3trial: material which is under very active development, for potential addition to l3kernel or l3experimental. Material in this directory may include potential replacements for existing modules, where large-scale changes are under-way. This code is not released to CTAN.
• l3leftovers: code which has been developed in the past by The LaTeX Project but is not suitable for use in its current form. Parts of this code may be used as the basis for new developments in l3kernel or l3experimental over time.

Support material for development is found in:

• support, which contains files for the automated test suite which are 'local' to the repository.

Documentation is found in:

• articles: discussion of concepts by team members for publication in TUGBoat or elsewhere.

The repository also contains the directory xpackages. This contain code which is being moved (broadly) l3experimental. Over time, xpackages is expected to be removed from the repository.

The issue tracker for expl3 is currently located on GitHub.

We use GitHub Actions as a hosted continuous integration service. For each commit, the build status is tested using the current release of TeX Live.

Current build status:

This code is developed by The LaTeX Project.

This README file is copyright 2021-2025 The LaTeX Project.