This is the documentation for the latest (main) development branch of Zephyr. If you are looking for the documentation of previous releases, use the drop-down list at the bottom of the left panel and select the desired version.

Project and Governance

The Zephyr project defines a development process workflow using GitHub Issues to track feature, enhancement, and bug reports together with GitHub Pull Requests (PRs) for submitting and reviewing changes. Zephyr community members work together to review these Issues and PRs, managing feature enhancements and quality improvements of Zephyr through its regular releases, as outlined in the program management overview.

We can only manage the volume of Issues and PRs, by requiring timely reviews, feedback, and responses from the community and contributors, both for initial submissions and for followup questions and clarifications. Read about the project’s development processes and tools and specifics about review timelines to learn about the project’s goals and guidelines for our active developer community.

TSC Project Roles describes in detail the Zephyr project roles and associated permissions with respect to the development process workflow.


  • mainline: The main tree where the core functionality and core features are being developed.

  • subsystem/feature branch: is a branch within the same repository. In our case, we will use the term branch also when referencing branches not in the same repository, which are a copy of a repository sharing the same history.

  • upstream: A parent branch the source code is based on. This is the branch you pull from and push to, basically your upstream.

  • LTS: Long Term Support