Firefox Nightly

About Firefox Nightly

Firefox Nightly is a pre-release development channel of the Firefox web browser, available for Windows, macOS, and Linux (including ARM64 builds). It receives daily updates reflecting features that have reached sufficient maturity for community testing and bug reporting, though listed features may or may not make it into a final Firefox release.

This version, 69.0a1, was first offered to Nightly channel users on May 20, 2019. It includes a change to how Windows allocates content process priority, giving more processor time to actively used tasks and less to background tasks (except video and audio playback), and adds download progress display in macOS Finder for files being downloaded. The "Always Activate" Flash option was removed, so Firefox now always asks for user permission before activating Flash on a website. Users who customize Firefox with userChrome.css or userContent.css files may need to manually enable the toolkit.legacyUserProfileCustomizations.stylesheets preference for those files to load.

Firefox Nightly is intended for developers and users who want to test upcoming features and file bug reports via Bugzilla. Firefox ESR (Extended Support Release) is offered as an alternative for users on unsupported systems, including Windows 8.1 and below or macOS 10.14 and below.

Key features

• Windows content process priority hints to prioritize active tasks over background processes
• Finder on macOS displays download progress for files being downloaded
• Flash requires explicit user permission before activating on any website
• Available for Windows (64-bit, 32-bit, ARM64), macOS, and Linux (64-bit, ARM64)

Frequently asked questions