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.


Zephyr project is provided as source code and build scripts for different target architectures and configurations, and not as a binary image. Updated versions of the Zephyr project are released approximately every four months.

All Zephyr project source code is maintained in a GitHub repository. In order to use a released version of the Zephyr project, it is recommended that you use West (Zephyr’s meta-tool) to Get Zephyr and install Python dependencies of the release you are interested in.

The technical documentation for current and past releases is available at (use the version selector to select your release of interest).

Release Life Cycle and Maintenance

Periodic Releases

The Zephyr project provides periodic releases every 4 months leading to the long term support releases approximately every 2 years. Periodic and non-LTS releases are maintained with updates, bug fixes and security related updates for at least two cycles, meaning that the project supports the most recent two releases in addition to the most recent LTS.

Long Term Support and Maintenance

A Zephyr Long Term Support (LTS) release is published every 2 years and is branched and maintained independently from the main tree for at least 2.5 years after it was released.

Support and maintenance for an LTS release stops at least half a year after the following LTS release is published.

Security Fixes

Each security issue fixed within Zephyr is backported or submitted to the following releases:

  • Currently supported Long Term Support (LTS) release.

  • The most recent two releases.

For more information, see Security Vulnerability Reporting.

Supported Releases


Release date


Zephyr 2.7.6



Zephyr 3.6.0



Zephyr 3.5.0



As of 2022-01-01, LTS1 (1.14.x) is not supported and has reached end of life (EOL).

Release Notes

Release notes contain a list of changes that have been made to the different areas of the project during the development cycle of the release. Changes that require the user to modify their own application to support the new release may be mentioned in the release notes, but the details regarding what needs to be changed are to be detailed in the release’s migration guide.

Migration Guides

Zephyr provides migration guides for all major releases, in order to assist users transition from the previous release.

As mentioned in the previous section, changes in the code that require an action (i.e. a modification of the source code or configuration files) on the part of the user in order to keep the existing behavior of their application belong in in the migration guide. This includes:

  • Breaking API changes

  • Deprecations

  • Devicetree or Kconfig changes that affect the user (changes to defaults, renames, etc)

  • Treewide changes that have an effect (e.g. changing the include path or defaulting to a different C standard library)

  • Anything else that can affect the compilation or runtime behavior of an existing application

Each entry in the migration guide must include a brief explanation of the change as well as refer to the Pull Request that introduced it, in order for the user to be able to understand the context of the change.