New

• Instant browser tab sharing through Hello

• GTK3 integration (GNU/Linux only)

• Synced Tabs button in button bar

• Tabs synced via Firefox Accounts from other devices are now shown in dropdown area of Awesome Bar when searching

• Introduce a new preference (network.dns.blockDotOnion) to allow blocking .onion at the DNS level

Fixed

• URLs containing a Unicode-format Internationalized Domain Name (IDN) are now properly redirected

Changed

• Tab Groups (Panorama) feature removed

Developer

• Inspector search now matches results from all content in the page, including subframes

• Ability to filter snapshot output in memory tool

• Support for diffing heap snapshots added to the memory tool

• Added Negative url filtering for the network monitor

• DOMContentLoaded and load events shown in the network monitor timeline

• List of animated properties and keyframes is now displayed when clicking on an animation in the animation-inspector’s timeline

• Fine tune animations by changing the playback rate of animations in the animation-inspector's timeline

HTML5

• Push API support, part of Progressive Web Apps

• Support delivery of a Content Security Policy (CSP) via a meta tag

• Web Speech synthesis API

• ES6 Classes