| Release Date | December 8, 2026 |
|---|---|
| Release Owner | Dianna Smith |
| Corresponding ESR releases | 153.5.0 |
| Nightly cycle length | 4 weeks |
| Beta cycle length | 4 weeks |
| Milestones | |
|---|---|
Deadline to request manual QAQA has been informed (via a Jira ticket) about features that require manual testing during the nightly and/or beta cycle. |
October 9 In 42.5 weeks |
Deadline to request accessibility engineering reviewAccessibility engineering review has been requested (using the |
October 9 In 42.5 weeks |
Nightly startsThe 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. |
October 12 In 43 weeks |
Build ready for QAFeatures 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. |
October 23?
In 44.5 weeks |
QA Test Plan approval dueThe 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. |
October 23 In 44.5 weeks |
Soft Code Freeze starts Draft beta release notesWe 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. |
November 5 In 46.5 weeks |
String Freeze startsIn 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. |
November 6 In 46.5 weeks |
QA pre-merge regression testing doneQA assess build readiness for shipping to Beta by running a set of Regression test cases and shares a test report. |
November 6 In 46.5 weeks |
Merge dayThis 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 158 and the beginning of our Beta stabilization cycle. |
November 9 In 47 weeks |
Beta 1 Go to buildBuilt manually just after the merge. It ships on Tuesday. Uplift requests are open. |
November 9 In 47 weeks |
Beta 1Rolled 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. |
November 10 In 47 weeks |
Beta 2First automated beta of the cycle. It is rolled out to 50% of our beta population. Build starts at 13:00 UTC. |
November 11 In 47.5 weeks |
Beta 3Beta rollout bumped to 100% provided stability is good. Build starts at 13:00 UTC. Stabilization work via uplifts. |
November 13 In 47.5 weeks |
SUMO content creationUser 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 13 In 47.5 weeks |
Beta 4Build starts at 13:00 UTC. Stabilization work via uplifts. |
November 16 In 48 weeks |
Beta 5Build starts at 13:00 UTC. Stabilization work via uplifts. |
November 18 In 48.5 weeks |
Beta 6 Last early betaOn 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 20 In 48.5 weeks |
Beta 7Experimental features are no longer activated at compile time. Build starts at 13:00 UTC. Stabilization work via uplifts. |
November 23 In 49 weeks |
SUMO content localizationNew content on support.mozilla.org team is finalized, uploaded to the server and provided to our localization teams internationally. |
November 23 In 49 weeks |
Beta 8Last week of the beta cycle. Build starts at 13:00 UTC. Stabilization work via uplifts. |
November 25 In 49.5 weeks |
Pre-release QA sign-offA 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 25 In 49.5 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 ( |
November 27 In 49.5 weeks |
Release Candidate Go to buildWe 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. |
November 30 In 50 weeks |
Release Candidate Release notes finalizedOur Release Candidate is shipped to all of our beta population. |
December 1 In 50 weeks |
Release day!We ship Firefox 158 at 14:00 UTC (6AM PST) at 25% rollout. |
December 8 In 51 weeks |
Potential Android dot releaseOne 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. |
December 15 In 52 weeks |
Planned dot releaseTwo 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. |
December 22 In 53 weeks |
| Milestones | |
|---|---|
158.0 branch is createdThe |
November 27 |
158.0 release candidate is createdThe 158.0 release candidate is created based on the |
November 27 |
Preliminary QA sign off on 158.0QA gives a preliminary sign off on 158.0. 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. |
November 30 |
Final QA sign off on 158.0 Release notes readyQA gives its final sign off on 158.0. 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. |
December 1 |
158.0 sent to Apple StoreWe submit 158.0 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. |
December 1 |
158.1 branch is createdThe |
December 4 |
158.1 release candidate is createdThe 158.1 release candidate is created based on the |
December 4 |
158.0 is shipped158.0 is shipped on the Apple Store at 3:00 AM UTC with a phased 7 days rollout: |
December 7 |
Preliminary QA sign off on 158.1QA gives a preliminary sign off on 158.1. 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. |
December 7 |
Final QA sign off on 158.1 Release notes readyQA gives its final sign off on 158.1. 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. |
December 8 |
158.1 sent to Apple StoreWe submit 158.1 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. |
December 10 |
158.2 branch is createdThe |
December 11 |
158.2 release candidate is createdThe 158.2 release candidate is created based on the |
December 11 |
158.1 is shipped158.1 is shipped on the Apple Store at 3:00 AM UTC with a phased 7 days rollout: |
December 14 |
Preliminary QA sign off on 158.2QA gives a preliminary sign off on 158.2. 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. |
December 14 |
Final QA sign off on 158.2 Release notes readyQA gives its final sign off on 158.2. 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. |
December 15 |
158.2 sent to Apple StoreWe submit 158.2 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. |
December 17 |
158.3 branch is createdThe |
December 18 |
158.3 release candidate is createdThe 158.3 release candidate is created based on the |
December 18 |
158.2 is shipped158.2 is shipped on the Apple Store at 3:00 AM UTC with a phased 7 days rollout: |
December 21 |
Preliminary QA sign off on 158.3QA gives a preliminary sign off on 158.3. 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. |
December 21 |
Final QA sign off on 158.3 Release notes readyQA gives its final sign off on 158.3. 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. |
December 22 |
158.3 sent to Apple StoreWe submit 158.3 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. |
December 24 |
158.3 is shipped158.3 is shipped on the Apple Store at 3:00 AM UTC with a phased 7 days rollout: |
December 28 |