Soft code freeze for Firefox 147 starts on Thursday, December 4 @ 8am UTC

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Ryan VanderMeulen

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Dec 3, 2025, 8:23:05 AM (7 days ago) Dec 3
to dev-pl...@mozilla.org, Firefox Dev
Hello,
With Firefox 146 in the Release Candidate phase this week, we are nearing the end of the Nightly 147 cycle.

In order to avoid invalidating the testing we get out of late Nightly and to ensure that we can roll out Beta 147 to a wider audience with confidence next week, we'd like to ask that any risky changes be avoided from Thursday, December 4 until after the version bump to 148 on December 8.

Also, please be advised that string freeze for Firefox 147 begins Friday, December 5. In order to ensure that our localizers have adequate time to translate strings, please make sure that all string changes have landed by EOD Friday.

Some reminders for the soft code freeze period:

Do:
- Be ready to back out patches that cause crash spikes, new crashes, severe regressions
- Monitor new regressions and escalate merge blockers
- Support release management by prioritizing fixing of merge blockers

Do Not:
- Land a risky patch or a large patch
- Land new features (that affect the current Nightly version) — be mindful that code behind NIGHTLY_BUILD or RELEASE_OR_BETA ifdefs can lead to unexpected CI results
- Flip prefs that enable new Features that were untested in the Nightly cycle
- Plan to kick off new experiments that might impact a feature's merge readiness

Please let us know if you have any questions/concerns.

Thanks,
Ryan VanderMeulen
Firefox Release Manager

Ryan VanderMeulen

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Dec 8, 2025, 8:22:46 AM (2 days ago) Dec 8
to dev-pl...@mozilla.org, Firefox Dev
The version bump to 148 has now landed on firefox-main and the soft freeze period is over.

Thank you,

Ryan VanderMeulen
Firefox Release Manager
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