Firefox Developer Edition (eo) 151.0 download

Version 151.0beta, first offered to Beta channel users on April 22, 2026
Firefox Beta gets updated 3 times a week and as a consequence, the release notes for the Beta channel are updated continuously to reflect features that have reached sufficient maturity to benefit from community feedback and bug reports.
Warning: Features listed here may or may not make a final release of Firefox.
In addition to these release notes, you can follow ongoing development via the Firefox Trains website or our @FirefoxBeta Bluesky account.

New
- On macOS, URLs copied from iOS devices using Apple’s Universal Clipboard now paste correctly in Firefox.
- HTML <select> dropdowns now display as an OS-native menu on macOS, aligning their appearance and behavior with the rest of the system.
- The about:translations page is now accessible through the More Tools section of the Application Menu.
- Address Autofill is enabled for users in the Netherlands.
- With Firefox for Android you can now to swipe vertically over the toolbar to quickly see your list of tabs.
- Private Browsing Mode now has a new privacy feature that allows users to instantly clear all data from their current private session without closing the entire browser.
- Standard Enhanced Tracking Protection mode is getting increased protections against fingerprinting that limit the amount of information revealed about your computer and frustrating attempts to track you across websites.
- Local profile backups are now available on macOS and Linux, with support for restoring them across platforms.
- Local network access restrictions are now rolling out to all users. Firefox requires websites to request permission before connecting to devices on your local network or to apps and services on your device. Previously, this protection was limited to users with Enhanced Tracking Protection set to Strict.
- You can now merge multiple PDFs directly in the Firefox PDF viewer.
- Added an AI Controls section to the Firefox for Android Settings for managing AI-enhanced features.
- High dynamic range video is now supported in Firefox on Windows 10 and 11 for HDR displays connected to AMD and NVIDIA GPUs (notably this excludes Intel+NVIDIA laptops for now), work is underway to enable this feature on more GPU vendors. To use this feature you must ensure that HDR mode is enabled for the relevant displays in Windows Settings - Display. HDR videos may appear brighter in Firefox than in other browsers, which will be improved in a future release, as well as optimizations for performance.

Fixed
- Correct screen resolution reporting via JS APIs in multiple monitor setups.
- Improved color management for copied and pasted images on macOS.
- Fixed an issue on macOS where maximized Firefox windows could reopen on the wrong monitor after relaunching in multi-display setups.

Changed
- 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.

Developer

Web Platform
- 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.
- Updated the behavior of implicit anchors in CSS Anchor Positioning. The position-anchor property now defaults to normal. When using position-area, implicit anchors are applied automatically, while popovers using anchor() or anchor-center now require position-anchor: auto to opt in.