Release notes tell you what new features and fixes have shipped in your version of Firefox.
Latest Firefox ESR version
To see release notes for the latest Firefox Extended Support Release (ESR) version, see latest Firefox ESR release notes.
Latest regular Firefox version
To see release notes for the latest regular version of Firefox, see latest Firefox release notes.
All Firefox versions
To see all Firefox release notes listed by version, see all Firefox release notes.
Enterprise release notes at Mozilla Support
Starting with Firefox version 78, Firefox release notes for issues that impact enterprises, including bug fixes, enhancements, and policy changes, are available at Mozilla Support. See Release notes - Firefox for Enterprise Help.