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Release DateApril 20, 2027
Release OwnerDianna Smith
Corresponding ESR releases 153.17.0
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.

March 11
In 20 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.

March 18
In 21 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.

March 18
In 21 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.

March 25
In 22 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.

March 26
In 22 weeks
Strings hand-off to engineering

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

March 29
In 22.5 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.

March 31
In 23 weeks
Nightly QA sign-off

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

March 31
In 23 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.

April 1
In 23 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 170 and the beginning of our Beta stabilization cycle.

April 1
In 23 weeks
Beta 1

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

April 5
In 23.5 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.

April 7
In 24 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.

April 8
In 24 weeks
Beta 3

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

April 9?
In 24 weeks
Beta 4

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

April 12
In 24.5 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.

April 13
In 24.5 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.

April 14
In 25 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.

April 15
In 25 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.

April 15
In 25 weeks
Release day!

Firefox 170 ships at 13:00 UTC (6 AM PT) with an initial 25% rollout.

April 20
In 25.5 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.

April 27
In 26.5 weeks
Milestones
170.0 branch is created

The firefox-v170.0 branch is created from the main branch. version.txt is bumped to 170.1 on main. Any further code change for the 170.0 release now requires an uplift request.

April 9
170.0 release candidate is created

The 170.0 release candidate is created based on the firefox-v170.0 branch. This build might contain additional uplifts. Additionaly, the 169.3 release is tagged as shipped.

April 9
Preliminary QA sign off on 170.0

QA gives a preliminary sign off on 170.0. 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.

April 12
Final QA sign off on 170.0 Release notes ready

QA gives its final sign off on 170.0. 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.

April 13
170.0 sent to Apple Store

We submit 170.0 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.

April 13
170.1 branch is created

The firefox-v170.1 branch is created from the main branch. version.txt is bumped to 171.0 on main. Any further code change for the 170.1 release now requires an uplift request.

April 16
170.1 release candidate is created

The 170.1 release candidate is created based on the firefox-v170.0 branch. This build might contain additional uplifts. Additionaly, the 170.0 release is tagged as shipped.

April 16
170.0 is shipped

170.0 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%.

April 19
Preliminary QA sign off on 170.1

QA gives a preliminary sign off on 170.1. 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.

April 19
Final QA sign off on 170.1 Release notes ready

QA gives its final sign off on 170.1. 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.

April 20
170.1 sent to Apple Store

We submit 170.1 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.

April 22
170.1 is shipped

170.1 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%.

April 26