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Release DateNovember 26, 2024
Release OwnerRyan VanderMeulen
Nightly cycle length4 weeks
Beta cycle length4 weeks
Corresponding ESR release 128.5.0
Desktop & Android
Nightly starts

The first day of the cycle is Merge Day. After merging mozilla-central to mozilla-beta, we bump the nightly version number on mozilla-central and a new development cycle starts for Firefox. A new Firefox Nightly is shipped every 12 hours.

September 30
Deadline to request manual QA

QA has been informed (via a Jira ticket) about features that require manual testing during the nightly and/or beta cycle.
Feature technical documentation is also required to draft Test Plans and Test Cases.

October 4
Build ready for QA in nightly

Features with a QA request are ready for testing to assess feature quality and provide a formal test report by the end of Week 3 of the nightly cycle.

October 11
Build ready for QA in beta

If nightly testing was skipped then features should be in a testable state by this date for beta testing.

October 23
Soft Code Freeze starts Draft beta release notes

We are nearing the end of the nightly cycle. Don't land new untested features. Risky changes should be avoided after 8:00 AM UTC until after the nightly version bump on Merge Day.

October 24
String Freeze starts

In order to ensure that our localizers have adequate time to translate strings, please make sure that all string changes have landed by end of day.

October 25
QA pre-merge regression testing done

QA assess build readiness for shipping to Beta by running a set of Regression test cases and shares a test report. Nightly Regression coverage is limited compared to Beta Regression testing throughout the Beta cycle.

October 25
Merge day

This is the day in the release cycle when we merge mozilla-central into mozilla-beta. This is the end of the development cycle for Firefox 133 and the beginning of our Beta stabilization cycle.

October 28
Beta 1 Go to build

Built manually just after the merge. It is rolled out to 25% of our beta population. Some experimental features are still activated to watch their behavior on a wider population. These experimental features will be deactivated mid-cycle. Uplift requests are open.

October 28
Beta 2 Go to build

First automated beta of the cycle. It is rolled out to 50% of our beta population. Build starts at 13:00 UTC.
Stabilization work via uplifts.

October 30
Beta 3 Go to build

Beta rollout bumped to 100% provided stability is good. Build starts at 13:00 UTC. Stabilization work via uplifts.

November 1
SUMO content creation

User affecting changes were identified and provided to the support.mozilla.org team. The support content for this release can now be created and will be translated before RC week.

November 1
Beta 4 Go to build

Build starts at 13:00 UTC. Stabilization work via uplifts.

November 4
Beta 5 Go to build

Build starts at 13:00 UTC. Stabilization work via uplifts.

November 6
Beta 6 Go to build Last early beta

On a regular 4 weeks beta cycle, Beta 6 is the last beta with experimental features still activated. Build starts at 13:00 UTC. Stabilization work via uplifts.

November 8
Beta 7 Go to build

Experimental features are no longer activated at compile time. Build starts at 13:00 UTC. Stabilization work via uplifts.

November 11
SUMO content localization

New content on support.mozilla.org team is finalized, uploaded to the server and provided to our localization teams internationally.

November 11
Beta 8 Go to build

Last week of the beta cycle. Build starts at 13:00 UTC. Stabilization work via uplifts.

November 13
Pre-release QA sign-off

A week before the final sign-off, QA shares preliminary test reports for each feature riding the train. This pre-release sign-off can be Green, Yellow or Red.

November 13
Beta 9 Go to build Last beta uplifts

On a regular 4 weeks beta cycle, this is the last beta and thus the end of beta uplifts. Build starts at 13:00 UTC.

November 15
Release Candidate Go to build

We merge our mozilla-beta repository to mozilla-release and close mozilla-beta until the next merge day. We then build our Release Candidate from mozilla-release. This is the build we intend to ship a week later unless we need to build a second Release Candidate to fix a major quality or business critical issue.

November 18
Release Candidate Release notes finalized

Our Release Candidate is shipped to all of our beta population.

November 19
Release day!

We ship Firefox 133 at 14:00 UTC (6AM PST) at 25% rollout.

November 26
Planned dot release

Two weeks after the release, we ship a dot release to address identified quality issues if needed. We may have to ship other dot releases before that date. If this is the case and post-release quality issues are already fixed and shipped, the decision on shipping or not the planned dot release is on the release management team.

December 10