Firefox Beta and Developer Edition
Release Notes

Correct screen resolution reporting via JS APIs in multiple monitor setups.

Improved color management for copied and pasted images on macOS.

The search bar in Firefox Settings (about:preferences) is now larger and spans the full Settings column, making it easier for users to search within Settings.

Geolocation on Windows now respects the user's Windows location permission setting, instead of overriding it, when the user grants location permission to a page. Firefox will ask users to enable the Windows permission if it is needed.

Extensions and Themes installed in a Firefox Desktop profile directory will be restored successfully after the profile directory is moved (or restored) to a different location or a different operating system.

A new CSSContainerRule.conditions property was introduced, holding an array of all container query conditions. This new property is intended to replace CSSContainerRule.containerName and CSSContainerRule.containerQuery, which only supported a single name and query, making them obsolete.

@container rules now allow specifying a list of container query conditions instead of just one condition.

Temporary site permissions are now correctly reflected in the Permissions API.

Firefox improves the rendering of absolutely positioned elements across multi-column containers and in printing, ensuring a more accurate element positioning and fragmentation.

Firefox now supports the declarative definition of slot assignment behaviour for shadow roots.

Container style queries are now supported allowing to apply styles to an element based on the computed values of custom properties of their container. This can be done by using one or more style() functions inside @container rules.

Firefox now supports the Document Picture-in-Picture API, which allows web pages to place content in an always-on-top popup.

The new Fullscreen Keyboard Lock API adds an optional argument to requestFullscreen that allows websites to request that while fullscreen, pressing the Escape key will no longer exit fullscreen (instead, a long-press is required), and certain formerly-reserved browser hotkeys are allowed to be default-prevented.

You can now manage microcontrollers that support serial communications in Firefox via the Web Serial API. This lets you program Microcontrollers and development boards, such as ESP devices, BBCmicro:bit and Raspberry Pi Picos, 3D printers & CNC machines, and other supported devices.