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Release DateDecember 14, 2027
Release OwnerRyan VanderMeulen
Corresponding ESR releases 175.12.0
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.

November 4
In 54 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.

November 10
In 54.5 weeks
Nightly starts

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

November 10
In 54.5 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.

November 18
In 56 weeks
QA Test Case review

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.

November 19
In 56 weeks
Strings hand-off to engineering

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

November 22
In 56.5 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.

November 24
In 56.5 weeks
Nightly QA sign-off

QA signs off on new features in Nightly by sharing individual test reports with their quality assessment and reasoning.

November 24
In 56.5 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.

November 25
In 57 weeks
Merge day

This is the day in the release cycle when we merge firefox-main into the beta branch. This is the end of the development cycle for Firefox 187 and the beginning of our Beta stabilization cycle.

November 25
In 57 weeks
Beta 1

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

November 29
In 57.5 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.

December 1
In 57.5 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 before release day.

December 2
In 58 weeks
Beta 3

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

December 3
In 58 weeks
Beta 4

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

December 6
In 58.5 weeks
Deadline to request security bug uplifts ESR patches must be ready

Deadline for security bugs uplift requests (sec-approval+ on Bugzilla).
ESR releases go to build on this day, before the last beta and the Release Candidate. Patches for security bugs affecting ESR branches must therefore be ready by this deadline.

December 7
In 58.5 weeks
Beta 5 Last beta uplifts

Last beta of the cycle and thus the end of beta uplifts. Build starts at 13:00 UTC.
After beta 5, we merge the beta branch to the release branch and close beta until the next merge day. We then build our Release Candidate from release.

December 8
In 58.5 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.

December 9
In 59 weeks
Release Candidate Ready for QA

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.

December 9
In 59 weeks
Release day!

Firefox 187 ships at 14:00 UTC (6 AM PT) with an initial 25% rollout.

December 14
In 59.5 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.

December 21
In 60.5 weeks
Milestones
187.0 branch is created

The firefox-v187.0 branch is created from the main branch. version.txt is bumped to 187.1 on main. Any further code change for the 187.0 release now requires an uplift request.

December 3
187.0 release candidate is created

The 187.0 release candidate is created based on the firefox-v187.0 branch. This build might contain additional uplifts. Additionaly, the 186.3 release is tagged as shipped.

December 3
Preliminary QA sign off on 187.0

QA gives a preliminary sign off on 187.0. 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.

December 6
Final QA sign off on 187.0 Release notes ready

QA gives its final sign off on 187.0. 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 7
187.0 sent to Apple Store

We submit 187.0 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 7
187.1 branch is created

The firefox-v187.1 branch is created from the main branch. version.txt is bumped to 188.0 on main. Any further code change for the 187.1 release now requires an uplift request.

December 10
187.1 release candidate is created

The 187.1 release candidate is created based on the firefox-v187.0 branch. This build might contain additional uplifts. Additionaly, the 187.0 release is tagged as shipped.

December 10
187.0 is shipped

187.0 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%.

December 13
Preliminary QA sign off on 187.1

QA gives a preliminary sign off on 187.1. 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 13
Final QA sign off on 187.1 Release notes ready

QA gives its final sign off on 187.1. 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 14
187.1 sent to Apple Store

We submit 187.1 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 16
187.1 is shipped

187.1 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%.

December 20