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Release DateSeptember 15, 2026
Release OwnerDonal Meehan
Corresponding ESR releases 153.3.0 · 140.16.0 · 115.41.0?
Nightly cycle length2 weeks
Beta cycle length2 weeks
Milestones
Deadline to request manual QA

QA has been informed via a Jira ticket (Functional, Nimbus/Remote delivery or Embedded QA) about features needing manual testing — more on how to file a Jira ticket here. Test Plans and Cases also require the technical documentation, which should be attached to the ticket.

August 6
In 2 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 13
In 3 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 13
In 3 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 21
In 4 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 21
In 4 weeks
Strings hand-off to engineering

Final strings are handed off to Engineering to ensure they are landed before localization begins.

August 26
In 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.

August 26
In 5 weeks
Draft beta release notes

A draft document was created and shared internally with stakeholders to prepare our final release notes for general availability. This document initially contains a copy of our public beta release notes shipping the week after and will be enriched during the beta cycle with media and final copy.

August 27
In 5 weeks
Nightly QA sign-off

QA signs off on the Nightly build, assessing its readiness for shipping to Beta by running a set of regression test cases and sharing a test report.

August 27
In 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.

August 27
In 5 weeks
Beta 1

First beta of the cycle, rolled out to our beta population. Build starts at 13:00 UTC. Stabilization work via uplifts.

August 31
In 5.5 weeks
Beta 2

First automated beta of the cycle. It is rolled out to 100% of our beta population. Build starts at 13:00 UTC.
Stabilization work via uplifts.

September 2
In 6 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 before release day.

September 2
In 6 weeks
Beta 3

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

September 4
In 6 weeks
Beta 4

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

September 7
In 6.5 weeks
Beta 5 Security bugs uplift request deadline Last beta uplifts

Last beta of the cycle and thus the end of beta uplifts. This is also the deadline for security bugs uplift requests (sec-approval+ on Bugzilla). Build starts at 13:00 UTC.

September 9
In 7 weeks
Release notes submission deadline

All release notes for Firefox were added to the draft document or communicated directly with the release manager. Illustrations such as screenshots and videos were provided. Final Release release notes are created by the release manager on firefox.com.

September 10
In 7 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.

September 10
In 7 weeks
Release day!

Firefox 156 ships at 13:00 UTC (6 AM PT) with an initial 25% rollout.

September 15
In 7.5 weeks
Dot release 1

Scheduled for one week after launch, this Desktop and/or Android release targets critical quality fixes and selective feature uplifts. The deadline for uplift requests is EOD on the Friday prior to go-live. Should emergency dot releases ship earlier and resolve pending issues, the Release Management team will determine if this scheduled milestone remains necessary.

September 22
In 8.5 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.

September 4
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.

September 4
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.

September 7
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.

September 8
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.

September 8
156.1 branch is created

The firefox-v156.1 branch is created from the main branch. version.txt is bumped to 157.0 on main. Any further code change for the 156.1 release now requires an uplift request.

September 11
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.

September 11
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%.

September 14
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.

September 14
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.

September 15
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.

September 17
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%.

September 21