.. _zephyr_release_notes:

Releases
########

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 six 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
:ref:`west` to :ref:`get_the_code` of the release you are interested in.

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

.. _zephyr_release_cycle:

Release Life Cycle and Maintenance
**********************************

Major and Maintenance Release Cadence
=====================================

The Zephyr Project delivers major releases using a six month cadence roughly timed
each April and October of the year.

This timescale facilitates regular releases that have strong QA cycles while
not overwhelming users with too many new releases.

The cadence is predictable and avoids many major holidays in various geographies.

The Zephyr project delivers maintenance releases on an unscheduled basis and
are usually driven by the accumulation of enough significant fixes or enhancements
to the associated major release.

The point release indicates a point in the major release branch where a full QA
cycle and release process validates the content of the new branch.

Long Term Support and Maintenance
=================================

While stable releases are supported for the duration of 2 release cycles (roughly 1 year),
some specific ones will be supported for a longer period by the Zephyr Project,
and are called Long Term Support (LTS) releases.

A Zephyr :ref:`Long Term Support (LTS) <release_process_lts>` release is
published every 2.5 to 3 years and is branched and maintained independently from the
main tree for approximately 5 years after it was released.

This offers more stability to project users and leaves more time to
upgrade to the following LTS release.


Transitioning to the new Release Cadence
========================================

The transition to the new release cadence will begin in 2026. Zephyr 4.4 is scheduled
for release in April 2026, and subsequent releases will occur every six months.

The projected timeline for upcoming releases is as follows:

+---------+-------------------+---------------------+
| Release | Planned Date      | Notes               |
+=========+===================+=====================+
| 4.4     | April 2026        |                     |
+---------+-------------------+---------------------+
| 4.5     | October 2026      |                     |
+---------+-------------------+---------------------+
| 4.6     | April 2027        | LTS4                |
+---------+-------------------+---------------------+
| 5.0     | October 2027      | Start of 5.x cycle  |
+---------+-------------------+---------------------+
| 5.1     | April 2028        |                     |
+---------+-------------------+---------------------+
| 5.2     | October 2028      |                     |
+---------+-------------------+---------------------+
| 5.3     | April 2029        |                     |
+---------+-------------------+---------------------+
| 5.4     | October 2029      | LTS5                |
+---------+-------------------+---------------------+

Starting with the 5.x release cycle, all releases will follow the new six-month
cadence from the beginning.


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  :ref:`Security Vulnerability Reporting <reporting>`.

.. _supported_releases:

Supported Releases
******************

+------------------------+----------------+---------------+
| Release                | Release date   | EOL           |
+========================+================+===============+
| `Zephyr 4.3.0`_        | 2025-11-14     | 2026-10-15    |
+------------------------+----------------+---------------+
| `Zephyr 4.2.0`_        | 2025-07-18     | 2026-03-20    |
+------------------------+----------------+---------------+
| `Zephyr 3.7.0 (LTS3)`_ | 2024-07-26     | 2029-07-27    |
+------------------------+----------------+---------------+

Previous LTS
************

+-------------------------+---------------+
| Release                 | EOL           |
+=========================+===============+
| `Zephyr 2.7.6 (LTS2)`_  | 2025-01-26    |
+-------------------------+---------------+
| `Zephyr 1.14.1 (LTS1)`_ | 2022-01-01    |
+-------------------------+---------------+

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.

Updates to the release notes post release cycle is permitted but limited to
style, typographical fixes and to upmerge the notes from maintenance release
branches with the sole purpose of keeping the latest documentation consistent
with the changes in the project.

.. toctree::
   :maxdepth: 1
   :glob:
   :reversed:

   release-notes-3.7
   release-notes-4.[2-4]

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.

.. toctree::
   :maxdepth: 1
   :glob:
   :reversed:

   migration-guide-3.7
   migration-guide-4.[2-4]

End-of-life Releases
********************

.. toctree::
   :hidden:
   :maxdepth: 1

   eol_releases

Release notes and migration guides for end-of-life releases of Zephyr RTOS can be accessed
:ref:`here <eol_releases>`.

.. _`GitHub repository`: https://github.com/zephyrproject-rtos/zephyr
.. _`GitHub tagged releases`: https://github.com/zephyrproject-rtos/zephyr/tags
.. _`Zephyr 1.14.1 (LTS1)`: https://docs.zephyrproject.org/1.14.1/
.. _`Zephyr 2.7.6 (LTS2)`: https://docs.zephyrproject.org/2.7.6/
.. _`Zephyr 3.7.0 (LTS3)`: https://docs.zephyrproject.org/3.7.0/
.. _`Zephyr 4.2.0`: https://docs.zephyrproject.org/4.2.0/
.. _`Zephyr 4.3.0`: https://docs.zephyrproject.org/4.3.0/
