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We have a lot of internal jargon, acronyms and internal project names at Mozilla. This glossary lists some of the key terms we use in the Release Management team.


Short for Chemical Spill. A chemspill is a rapid security-driven dot release of our product.


Name of the project that removed the intermediary channel called Aurora which existed between Nightly and Beta so as to reduce our release time. You can read more about it on the Release Management blog: Dawn project or the end of Aurora.

Dot release

A minor release in which only the version number behind the dot is changed, hence its name. Ex: Major Release 60 Dot Release is 60.0.1

Dot releases are usually done to fix a stability (top-crash) or a security (Chemspill) issue and are done outside of the usual release dates.


Acronym for Go to build . Mostly used in the release schecule communication ("Go to build on March 18"), this means that we initiate the building of a specific release.

Merge Day

This is the day in the release cycle when we merge mozilla-central into mozilla-beta and mozilla-beta into mozilla-release. That both means the release of a new version of Firefox and the beginning of a new development cycle on mozilla-central (the version numbers on mozilla-central and mozilla-release are bumped up). During the cycle, there is a first merge of mozilla-central into mozilla-beta used to produce Dev Edition Beta 1 and 2, this is called the "first merge". During the first merge, the version number on mozilla-central is not bumped.

Nightly soft code freeze

Last week of the nightly cycle on mozilla-central justr before the merge to beta during which landing risky or experimental code in the repository is discouraged.


Name of the internal application used by release managers to prepare and publish release notes. The data in this application is fetched by


Acronym for Release-drivers.


Short for Release Engineering.


Short for Release Management.


Short for Release notes.


Acronym for Regression Engineering Owner


Name of the internal application used by release management to store all the metadata relevant to a release (version, code and l10n shas, date, platforms, chemspill or not…) and make it available to release engineering tools for releases. The data is also exposed publicly as JSON files as part of a public API called [[1]].

String Freeze

Period during which the introduction, modification or deletion of strings exposed to the end-users is not allowed so as to allow our localizers to translate our product.


Internal name of the web application which processes crash data at

Train Model

Our release process Mozilla has a fixed-schedule release model known as the Train Model, in which we release Firefox every six to eight weeks. Since 2016 we have a "flexible train model" which means that we still plan release dates but adjust the length of each cycle during the year to meet internal and market needs.


Short for "what's new pages". The page that is displayed in our product when they get a major update. These pages are hosted on for our Desktop products and on Google Play, Apple AppStore and other software stores for mobile.