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The 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.

QA has been informed (via a Jira ticket) about features that require manual testing during the nightly and/or beta cycle.
Feature technical documentation is also required to draft Test Plans and Test Cases.

Features with a QA request are ready for testing to assess feature quality and provide a formal test report by the end of Week 3 of the nightly cycle.

If nightly testing was skipped then features should be in a testable state by this date for beta testing.

We 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.

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.

QA assess build readiness for shipping to Beta by running a set of Regression test cases and shares a test report. Nightly Regression coverage is limited compared to Beta Regression testing throughout the Beta cycle.

This 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 119 and the beginning of our Beta stabilization cycle.

Built manually just after the merge. It is rolled 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. Uplift requests are open.

First automated beta of the cycle. It is rolled out to 50% of our beta population. Build starts at 13:00 UTC.
Stabilization work via uplifts.

Beta rollout bumped to 100% provided stability is good. Build starts at 13:00 UTC. Stabilization work via uplifts.

User 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.