Firefox Beta and Developer Edition
Release Notes

Avoided always posting a NSEvent to the event loop every time a non-native event is ran which should reduce the CPU usage of the WindowServer process.

The Picture-in-Picture toggle button can now be moved to the opposite side of the video from the new context menu option Move Picture-in-Picture Toggle to Left (Right) Side.

Reduced power usage of software decoded video on macOS especially in fullscreen. This includes many streaming sites like Netflix or Amazon Prime Video.

RLBox — a new technology that hardens Firefox against potential security vulnerabilities in third-party libraries — is now enabled on all platforms.

We’ve added a User Agent override for Slack.com, which allows Firefox users to use more Call features and have access to Huddles.

On macOS command-clicking links in Gmail still does not open a new tab. Workaround: you can click links in Gmail without pressing command, which will still open a new tab.