Milestones and key data for Firefox 151

Release Date	May 19, 2026
Release Owner	Donal Meehan
Corresponding ESR releases	140.11.0 · 115.36.0^?
Nightly cycle length	4 weeks
Beta cycle length	4 weeks
Bugs fixed in nightly	2691
Uplifts in beta	388 (0 backouts)
Uplifts in RC	2 (0 backouts)
Uplifts in dot releases	0 (0 backouts)
Total number of uplifts	390
Betas	10
Release Candidates	2
Dot releases	0
Release notes	General · Developer · Enterprise

Key Milestones
Nightly start	March 24
Beta start	April 22
151.0 ^{0% adoption - 25% rollout}	May 19
Planned 151.0.x ^{Desktop and Android}	May 26
Planned 151.0.x ^{Desktop and Android}	June 2
Planned 151.0.x ^{Desktop and Android}	June 9

Milestones
151.0 branch is created The `firefox-v151.0` branch is created from the `main` branch. `version.txt` is bumped to 151.1 on `main`. Any further code change for the 151.0 release now requires an uplift request.	May 8
151.0 release candidate is created The 151.0 release candidate is created based on the `firefox-v151.0` branch. This build might contain additional uplifts. Additionaly, the 150.3 release is tagged as shipped.	May 8
Preliminary QA sign off on 151.0 QA gives a preliminary sign off on 151.0. 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.	May 11
Final QA sign off on 151.0 Release notes ready QA gives its final sign off on 151.0. 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.	May 12
151.0 sent to Apple Store We submit 151.0 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.	May 12
151.1 branch is created The `firefox-v151.1` branch is created from the `main` branch. `version.txt` is bumped to 151.2 on `main`. Any further code change for the 151.1 release now requires an uplift request.	May 15
151.1 release candidate is created The 151.1 release candidate is created based on the `firefox-v151.0` branch. This build might contain additional uplifts. Additionaly, the 151.0 release is tagged as shipped.	May 15
151.0 is shipped 151.0 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%.	May 18
Preliminary QA sign off on 151.1 QA gives a preliminary sign off on 151.1. 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.	May 18
Final QA sign off on 151.1 Release notes ready QA gives its final sign off on 151.1. 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.	May 19
151.1 sent to Apple Store We submit 151.1 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.	May 21
151.2 branch is created The `firefox-v151.2` branch is created from the `main` branch. `version.txt` is bumped to 151.3 on `main`. Any further code change for the 151.2 release now requires an uplift request.	May 22
151.2 release candidate is created The 151.2 release candidate is created based on the `firefox-v151.0` branch. This build might contain additional uplifts. Additionaly, the 151.1 release is tagged as shipped.	May 22
151.1 is shipped 151.1 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%.	May 25
Preliminary QA sign off on 151.2 QA gives a preliminary sign off on 151.2. 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.	May 25
Final QA sign off on 151.2 Release notes ready QA gives its final sign off on 151.2. 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.	May 26
151.2 sent to Apple Store We submit 151.2 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.	May 28
151.3 branch is created The `firefox-v151.3` branch is created from the `main` branch. `version.txt` is bumped to 152.0 on `main`. Any further code change for the 151.3 release now requires an uplift request.	May 29
151.3 release candidate is created The 151.3 release candidate is created based on the `firefox-v151.0` branch. This build might contain additional uplifts. Additionaly, the 151.2 release is tagged as shipped.	May 29
151.2 is shipped 151.2 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%.	June 1
Preliminary QA sign off on 151.3 QA gives a preliminary sign off on 151.3. 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.	June 1
Final QA sign off on 151.3 Release notes ready QA gives its final sign off on 151.3. 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.	June 2
151.3 sent to Apple Store We submit 151.3 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.	June 4
151.3 is shipped 151.3 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%.	June 8