Firefox Release Notes

Support for Google’s Widevine CDM on Windows and Mac OS X so streaming services like Amazon Video can switch from Silverlight to encrypted HTML5 video.

Enable VP9 video codec for users with fast machines

Embedded YouTube videos now play with HTML5 video if Flash is not installed.

Allow no-cache on back/forward navigations for https resources

Latgalu [ltg] locale added. Wikipedia tells us there are 164,500 daily speakers.

View and search open tabs from your smartphone or another computer in a sidebar

Various security fixes

FUEL (Firefox User Extension Library) has been removed. Add-ons relying on it will stop working.

The browser.sessionstore.restore_on_demand preference has been reset to its default value (true) to avoid e10s performance problems. Because faster is better!

The Firefox click-to-activate plugin whitelist has been removed.

XRender is no longer used for rendering web content on Linux as this may cause a regression in remote X performance

Smart multi-line input in the Web Console

Custom user agents supported in Responsive Design Mode

Simulate Push messages in the Service Workers developer tool

View, start,and debug registered Service Workers in the Service Workers developer tool

'Start' button for service workers in about:debugging to start registered Service Workers

Added support for ChaCha20/Poly1305 cipher suites

Changes that can affect add-on compatibility

Web platform changes

WebCrypto: RSA-PSS signature support

WebCrypto: PBKDF2 supports SHA-2 hash algorithms

cuechange events are now available on TextTrack objects

Known issue with old invalid paper size printing preferences (Bug 1276717)

Selenium WebDriver may cause Firefox to crash on startup, use Marionette WebDriver instead