.. _zephyr_release_notes:

Releases
########

Zephyr is distributed as source code and build scripts, not as a binary image.
Use :ref:`west` to :ref:`get the code <get_the_code>` for a specific version,
and see the `GitHub repository`_ for the full history of tagged releases.

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).

.. _supported_releases:

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

The table below lists all actively supported releases. For most users, the
recommended starting point is either the **latest stable release** or the
**current LTS release**.

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

   release-notes-3.7
   release-notes-4.[3-5]
   migration-guide-3.7
   migration-guide-4.[3-5]

.. note::
   | The next planned release is **Zephyr 4.5**, targeted for **October 2026**.
   | The working drafts of the associated :doc:`Release Notes <release-notes-4.5>`
     and :doc:`Migration Guide <migration-guide-4.5>` are already available.

.. list-table::
    :header-rows: 1

    * - Release
      - Release Date
      - EOL
      - Status
      - Supporting Documentation
    * - `Zephyr 4.4.0`_
      - 2026-04-14
      - 2027-04-12
      - Latest stable
      - * :doc:`Release Notes <release-notes-4.4>`
        * :doc:`Migration Guide <migration-guide-4.4>`
    * - `Zephyr 4.3.0`_
      - 2025-11-14
      - 2026-10-15
      - Stable
      - * :doc:`Release Notes <release-notes-4.3>`
        * :doc:`Migration Guide <migration-guide-4.3>`
    * - `Zephyr 3.7.0 (LTS3)`_
      - 2024-07-26
      - 2029-07-27
      - Long Term Support
      - * :doc:`Release Notes <release-notes-3.7>`
        * :doc:`Migration Guide <migration-guide-3.7>`

Previous LTS releases that have reached end-of-life:

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

End-of-life releases
=====================

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

   eol_releases

End-of-life releases are no longer maintained and do not receive security fixes.
The release notes and migration guides for these releases are available
:ref:`here <eol_releases>`.

.. _zephyr_release_cycle:

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

Major and Maintenance Releases
==============================

Zephyr delivers major releases on a **six-month cadence**, targeting April and
October each year. This schedule provides regular, well-tested releases without
overwhelming users with too-frequent updates, and avoids major holidays across
geographies.

Maintenance (point) releases are published on an unscheduled basis when enough
significant fixes have accumulated on a major release branch. Each point release
goes through a full QA cycle before publishing.

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>`.

Release documentation
*********************

Each release includes two companion documents:

- Release notes summarize changes made across the project during the release cycle.
- Migration guides describe changes that require action when moving an application from one major
  release to the next.

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.

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.

.. _`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 4.3.0`: https://docs.zephyrproject.org/4.3.0/
.. _`Zephyr 4.4.0`: https://docs.zephyrproject.org/4.4.0/