Version 63.0a1, first offered to Nightly channel users on June 25, 2018
Firefox Nightly gets updated every day and as a consequence, the release notes for the Nightly channel are updated continuously to reflect features that have reached sufficient maturity to benefit from community feedback and bug reports. Features listed here may or may not make a final release of Firefox.
In addition to these release notes, you can follow ongoing development on our @FirefoxNightly Twitter account as well as read our Nightly Blog.
WebExtensions now run in their own process on Linux
Firefox now warns about having multiple windows and tabs open when quitting from the main menu. The Save and Quit feature has been removed. You can restore your session by ticking the box for Restore previous session in the General → Startup options or by using Restore Previous Session in the main menu.
TLS certificates issued by Symantec are no longer trusted by Firefox Nightly. Website operators are strongly encouraged to replace any remaining Symantec TLS certificates before Firefox 63 final release on October 23.
The Ctrl+Tab shortcut now displays thumbnail previews of your tabs and cycles through tabs in recently used order. This new default behavior is activated only in new profiles and can be changed in preferences.