Firefox Beta and Developer Edition
Release Notes

The baseline interpreter for JavaScript bytecode execution is now enabled

The developer tools accessibility panel now includes an audit for keyboard accessibility

The developer tools accessibility panel now includes a color deficiency simulator for systems with WebRender enabled

When focused on a toolbar button, users can now type the first (or first few) characters of another button's name to jump directly to that button.

Inactive CSS: The Inspector now grays out CSS declarations that don’t affect the selected element and shows a tooltip explaining why.

macOS: Vastly reduced power consumption with a more efficient compositor

Built-in Firefox pages now follow the system dark mode preference

WebRender enabled by default for Windows desktops with Integrated Intel graphics for Low Resolution devices

Aliased theme properties have been removed, which may affect some themes

The Firefox Accounts toolbar menu has been updated and reorganized to give faster access to account features and services.

Write snippets of code and iterate on them faster in the WebConsole with the
new multi-line editor mode. The Enter key adds new lines like in a regular editor. Evaluate with Ctrl + Enter (Cmd + Enter on OSX).

Firefox now supports the CSS properties "text-decoration-thickness" and "text-underline-offset", which let web developers control the position and size of text decoration lines.
Firefox now supports the CSS property "text-decoration-skip-ink", which (by default) makes underlines and overlines skip over any text that they intersect, to improve readability.

DOM Breakpoints in Developer Tools allows diagnose with code in a page changes a specific DOM node, including the node's children