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Release DateOctober 13, 2026
Release OwnerDonal Meehan
Corresponding ESR releases 153.3.0
Nightly cycle length4 weeks
Beta cycle length4 weeks
Milestones
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.

August 14
In 34.5 weeks
Deadline to request accessibility engineering review

Accessibility engineering review has been requested (using the a11y-review flag on Bugzilla) for new (or significantly redesigned) UI that requires assessment to determine whether it is accessible to people with disabilities.

August 14
In 34.5 weeks
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.

August 17
In 35 weeks
Build ready for QA

Features with a QA request are ready for testing to assess feature quality and provide a formal test report by the end of Week 2 of the nightly cycle.

August 28?
In 36.5 weeks
QA Test Plan approval due

The QA team appreciates an earlier sign-off from the project teams. The approval milestone will be the final deadline for any feature Test Plan sign-offs. No feedback/sign-off on QAs Feature Test Plan could result in misalignment on testing scope, incomplete test coverage and invalid bugs.

August 28
In 36.5 weeks
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.

September 10
In 38.5 weeks
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.

September 11
In 38.5 weeks
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.

September 11
In 38.5 weeks
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 156 and the beginning of our Beta stabilization cycle.

September 14
In 39 weeks
Beta 1 Go to build

Built manually just after the merge. It ships on Tuesday. Uplift requests are open.

September 14
In 39 weeks
Beta 1

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.

September 15
In 39 weeks
Beta 2

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.

September 16
In 39.5 weeks
Beta 3

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

September 18
In 39.5 weeks
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.

September 18
In 39.5 weeks
Beta 4

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

September 21
In 40 weeks
Beta 5

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

September 23
In 40.5 weeks
Beta 6 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.

September 25
In 40.5 weeks
Beta 7

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

September 28
In 41 weeks
SUMO content localization

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

September 28
In 41 weeks
Beta 8

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

September 30
In 41.5 weeks
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.

September 30
In 41.5 weeks
Beta 9 Last beta uplifts (sec-approval request deadline)

On a regular 4 weeks beta cycle, this is the last beta and thus the end of beta uplifts, including security bugs for this release (sec-approval+ on Bugzilla). Build starts at 13:00 UTC.

October 2
In 41.5 weeks
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 another Release Candidate to fix a major quality or business critical issue.

October 5
In 42 weeks
Release Candidate Release notes finalized

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

October 6
In 42 weeks
Release day!

We ship Firefox 156 at 14:00 UTC (6AM PST) at 25% rollout.

October 13
In 43 weeks
Potential Android dot release

One week after the release, we evaluate shipping an Android dot release to address identified issues. We can also enable new features on a on a case by case basis if they are suitable for uplift. The decision on shipping or not this dot release for Android is on the release management team.

October 20
In 44 weeks
Planned dot release

Two weeks after the release, we ship a desktop and/or an Android dot release to address identified quality issues with safe fixes ready. We can also enable new features on a on a case by case basis if they are suitable for uplift. 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.

October 27
In 45 weeks
Milestones
156.0 branch is created

The firefox-v156.0 branch is created from the main branch. version.txt is bumped to 156.1 on main. Any further code change for the 156.0 release now requires an uplift request.

October 2
156.0 release candidate is created

The 156.0 release candidate is created based on the firefox-v156.0 branch. This build might contain additional uplifts. Additionaly, the 155.3 release is tagged as shipped.

October 2
Preliminary QA sign off on 156.0

QA gives a preliminary sign off on 156.0. If it is green, we push the build to the External Beta Testers group. Otherwise, the dev team fixes the issues reported by QA, uplift them to the release branch and we build another Release Candidate.

October 5
Final QA sign off on 156.0 Release notes ready

QA gives its final sign off on 156.0. If the sign off is red, the dev team fixes the issues reported by QA, uplift them to the release branch and we build another Release Candidate.

October 6
156.0 sent to Apple Store

We submit 156.0 for review to the Apple Store. If we don`t have a working build by the end of the day, we may not ship this week.

October 6
156.1 branch is created

The firefox-v156.1 branch is created from the main branch. version.txt is bumped to 156.2 on main. Any further code change for the 156.1 release now requires an uplift request.

October 9
156.1 release candidate is created

The 156.1 release candidate is created based on the firefox-v156.0 branch. This build might contain additional uplifts. Additionaly, the 156.0 release is tagged as shipped.

October 9
156.0 is shipped

156.0 is shipped on the Apple Store at 3:00 AM UTC with a phased 7 days rollout:
Monday: 1%, Tuesday: 2%, Wednesday: 5%, Thursday: 10%, Friday: 20%, Saturday: 50%, Sunday: 100%.

October 12
Preliminary QA sign off on 156.1

QA gives a preliminary sign off on 156.1. If it is green, we push the build to the External Beta Testers group. Otherwise, the dev team fixes the issues reported by QA, uplift them to the release branch and we build another Release Candidate.

October 12
Final QA sign off on 156.1 Release notes ready

QA gives its final sign off on 156.1. If the sign off is red, the dev team fixes the issues reported by QA, uplift them to the release branch and we build another Release Candidate.

October 13
156.1 sent to Apple Store

We submit 156.1 for review to the Apple Store. If we don`t have a working build by the end of the day, we may not ship this week.

October 15
156.2 branch is created

The firefox-v156.2 branch is created from the main branch. version.txt is bumped to 156.3 on main. Any further code change for the 156.2 release now requires an uplift request.

October 16
156.2 release candidate is created

The 156.2 release candidate is created based on the firefox-v156.0 branch. This build might contain additional uplifts. Additionaly, the 156.1 release is tagged as shipped.

October 16
156.1 is shipped

156.1 is shipped on the Apple Store at 3:00 AM UTC with a phased 7 days rollout:
Monday: 1%, Tuesday: 2%, Wednesday: 5%, Thursday: 10%, Friday: 20%, Saturday: 50%, Sunday: 100%.

October 19
Preliminary QA sign off on 156.2

QA gives a preliminary sign off on 156.2. If it is green, we push the build to the External Beta Testers group. Otherwise, the dev team fixes the issues reported by QA, uplift them to the release branch and we build another Release Candidate.

October 19
Final QA sign off on 156.2 Release notes ready

QA gives its final sign off on 156.2. If the sign off is red, the dev team fixes the issues reported by QA, uplift them to the release branch and we build another Release Candidate.

October 20
156.2 sent to Apple Store

We submit 156.2 for review to the Apple Store. If we don`t have a working build by the end of the day, we may not ship this week.

October 22
156.3 branch is created

The firefox-v156.3 branch is created from the main branch. version.txt is bumped to 157.0 on main. Any further code change for the 156.3 release now requires an uplift request.

October 22
156.3 release candidate is created

The 156.3 release candidate is created based on the firefox-v156.0 branch. This build might contain additional uplifts. Additionaly, the 156.2 release is tagged as shipped.

October 22
156.2 is shipped

156.2 is shipped on the Apple Store at 3:00 AM UTC with a phased 7 days rollout:
Monday: 1%, Tuesday: 2%, Wednesday: 5%, Thursday: 10%, Friday: 20%, Saturday: 50%, Sunday: 100%.

October 26
Preliminary QA sign off on 156.3

QA gives a preliminary sign off on 156.3. If it is green, we push the build to the External Beta Testers group. Otherwise, the dev team fixes the issues reported by QA, uplift them to the release branch and we build another Release Candidate.

October 26
Final QA sign off on 156.3 Release notes ready

QA gives its final sign off on 156.3. If the sign off is red, the dev team fixes the issues reported by QA, uplift them to the release branch and we build another Release Candidate.

October 27
156.3 sent to Apple Store

We submit 156.3 for review to the Apple Store. If we don`t have a working build by the end of the day, we may not ship this week.

October 29
156.3 is shipped

156.3 is shipped on the Apple Store at 3:00 AM UTC with a phased 7 days rollout:
Monday: 1%, Tuesday: 2%, Wednesday: 5%, Thursday: 10%, Friday: 20%, Saturday: 50%, Sunday: 100%.

November 2