Mozilla Release Notes

Version 151.0, first offered to Release channel users on May 19, 2026

New

Firefox Home (New Tab) has a fresh, new look and feel. The layout and design will enable upcoming features, from widgets to shortcuts improvements, launching between 151 and 152. Included are some new and exciting Wallpapers, such as the one below. Use the pencil icon in the lower right to check them out.

Private Browsing Mode now allows you to instantly clear all data from your current session without closing the entire window. When you select the End Private Session button (the fire icon) to the right of the URL bar, Firefox will ask you to confirm to clear your session. Once confirmed, it will wipe all of your private browsing data and open a fresh new Private Browsing Mode session for you.

Firefox now strengthens protection against fingerprinting in Standard Enhanced Tracking Protection, making it harder for websites to track you across sites by limiting the amount of information revealed about your device and browser. This reduces the number of users uniquely identifiable by common fingerprinting techniques by an average of ~14%, and by ~49% on macOS.

You can now merge multiple PDFs directly in the Firefox PDF viewer.

The Translations page (about:translations) is now accessible through the More Tools section of the Application Menu.

Local Firefox profile backups are now available on Linux in addition to Windows, and you can restore them across platforms.

On macOS, URLs copied from iOS devices using Apple’s Universal Clipboard now paste correctly in Firefox.

On macOS, dropdown menus on web pages now use the native macOS menu style, matching the look and behavior of the rest of the system.

Address Autofill is enabled for users in the Netherlands.

Firefox’s built-in VPN now lets you choose your browsing location, giving you more control over how and where your traffic appears online. You can select from available countries or use Recommended to automatically choose the best connection for your network.
This feature is part of a progressive roll out.

Fixed

Fixed incorrect screen resolution reporting to websites in multi-monitor setups.

Fixed an issue on macOS where maximized Firefox windows could reopen on the wrong monitor after relaunching in multi-monitor setups.

Improved color management for copied and pasted images on macOS.

Various security fixes.

Changed

The search bar in Firefox Settings (about:preferences) is now larger and spans the full width of the settings content area, making it easier to find options.

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.

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.

Enterprise

You can find information about policy updates and enterprise-specific bug fixes in the Firefox for Enterprise 151 Release Notes.

Developer

Developer Information

Web Platform

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, Raspberry Pi Picos, 3D printers, CNC machines, and other devices. Web Serial can be used in Extensions, but not from moz-extension contexts at this time.

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.
This feature is part of a progressive roll out.

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.

Firefox improves the rendering of absolutely positioned elements across multi-column containers and when printing, producing more accurate positioning and fragmentation.

@container rules now allow specifying a list of container query conditions rather than a single condition.

Firefox now supports container style queries, allowing styles to be applied to an element based on the computed values of its container's custom properties. This can be done by using one or more style() functions inside @container rules.

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 deprecated.

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.

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

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

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

Community Contributions

With the release of Firefox 151, we are pleased to welcome the developers who contributed their first code change to Firefox in this release, 37 of whom were brand new volunteers. Please join us in thanking each of these diligent and enthusiastic individuals, and take a look at their contributions:

Allison Embrey: 1938268
any1here: 2031162
aoia7rz7l: 1978290, 1984679
Armin Ulrich: 2031598
Brandon Lucier: 2030631
Chidimma Okoloigwe: 1901274
Chukwuka Rosemary: 1846829, 1948019, 2026574, 2028153
david.nicolson: 2026024
DrSeed: 1962904, 1968244, 1982888
EJiro Oghenekome: 1910902, 1938466, 1952061
gotyaoi: 1807516
Hailia: 2016934
Itoro James: 1936929, 2015491
japandi: 1977741, 1986020, 2015071
John Iweh: 1997925, 2027867
jonathancabera: 2012399, 2016058, 2026032
Keji Bakare: 2006572, 2008756, 2025287, 2031116
Kevin Doughty: 1984925
kofoworola shonuyi: 1999012, 2019901, 2028293
konyhéa: 1856191, 1876108, 1883497, 1891970, 2014334, 2030069
Mary cathline: 2022115
Miha Lepej [:lepko]: 2026335, 2029254
mozilla.7fhrv: 2023374
Noble Chinonso: 1945835, 1953621, 2019235, 2025701, 2028628
Okhuomon Ajayi: 2018272, 2026649, 2029684
Oluwatobi: 1975391, 2019936, 2023913
Osoble: 1876109
Philipp Hancke [:fippo]: 1056433, 2028060
Pranjali Srivastava: 944228, 1874155, 2009917
Rishan: 2030428
ROSHAAN: 1997346, 2018276, 2028927
Sameeksha: 2008178, 2021421
Sayd Mateen: 2021681
SuGotLand: 2025558
tk: 1826983
Vector: 2008128
wenzhao: 2031373

Original source

What’s New

• Enable Thundermail OAuth sign-in with account auto-configuration
• Enable users to override OAuth provider details for EWS accounts
• Tasks can be sorted by created or modified date

Changed

• Reinstated default application check when Thunderbird starts
• OpenPGP public key no longer attached by default in signed-only messages

Fixed

• Thunderbird could crash when processing message headers
• Thunderbird could crash on startup
• Calendar view tabs were not properly keyboard accessible
• Thunderbird could crash when processing new incoming messages
• On macOS, dragging attachments out of Thunderbird created multiple copies
• Cancelling a newsgroup posting was not possible
• Some IMAP emails showed current time instead of correct received date
• Search result count was missing when using 'Find in Message' or Ctrl+F
• Search results showed older irrelevant emails before newer exact matches
• Reply with selected text lost formatting for HTML messages containing </pre>
• Multipart/related attachments were not preserved when editing or forwarding
• Forwarded malformed MIME email had empty body and extra attachment
• OWL add-on description was not visible in Account Hub for non-en-US locales
• Account Hub prompted for password after OAuth login, causing Outlook setup failure
• Auto-discovered Account Hub values were not preserved for manual editing
• Account Hub links for encryption and signature opened the wrong account
• Virtual folders did not update correctly for filtered POP3 messages
• Thunderbird could crash in spam filtering
• Using thunderbird -compose with double quotes made last email address invalid
• With auto-mark-read disabled, large mail still marked as read during load delay
• It was not possible to create date-only all-day tasks
• Task context menu (right-click) had several disabled menu items
• 'Current Tasks' view showed past and finished tasks instead of only unfinished

Visual and UX improvements

Security fixes

As always, you’re encouraged to tell us what you think, ask for help, or file a bug in Bugzilla

Original source

Fixed

Fixed an issue where websites on internal or corporate networks that require a login prompt would show a blank page. (Bug 2034752)

Fixed an issue that prevented highlighting from working on scanned images in the built-in PDF viewer. (Bug 2034980)

Fixed an issue where the "New" badge persisted on Split View menu items. (Bug 2027793)

Fixed an issue that prevented some webcams from working correctly in video calls. (Bug 2034722)

Fixed an issue where a tab would crash when dragging and dropping nested folders onto a webpage. (Bug 2030461)

Improved how Firefox displays websites with advanced 3D effects, fixing cases where parts of the page could disappear or appear incorrectly. (Bug 2034283)

Fixed an issue that could prevent Firefox’s local backup feature from completing successfully. (Bug 2029240)

Fixed an issue where the status and navigation bars would flicker or show mismatched colors when editing a page’s address. (Bug 2021596)

Improved the appearance of search suggestions in the address bar by preventing icons from appearing stretched or distorted. (Bug 2035353)

Various security fixes.

Reference link to 150.0.1 release notes.

Original source

Version 150.0.1, first offered to Release channel users on April 28, 2026

Fixed

• Fixed an issue where Facebook and other websites might not load properly for users with Bitdefender security software installed. (Bug 2034178)
• Fixed an issue where denying a geolocation permission prompt could cause Firefox to show the system permission dialog again on a second attempt. (Bug 2034120)
• Fixed an issue that prevented tabs from being added to some older saved tab groups. (Bug 2031961)
• Fixed a layout issue where some drop-down menus expanded to display all list items at once. (Bug 2033117)
• Fixed an issue where borders and outlines on some page elements disappeared when pinch zooming or smart zooming on macOS and Windows. (Bug 2030043)
• Various security fixes.

Changed

• All Relay users can now create up to 50 email masks—an increase from the previous limit of 5.

Reference link to 150.0 release notes.

Original source

What’s New

'Recent Destinations' in General Settings now supports alphabetical sorting

Added support for generating Unobtrusive Signatures (OpenPGP)

Message body search enabled for OpenPGP and S/MIME encrypted messages

Account hub is opened on the first run of Thunderbird

Address book cards can be copied to the clipboard as vCard

Custom Accent Color can be chosen in Appearance Settings

Calendar month/multiweek views are now scrollable with touch screen

PDF pages can be reorganized directly in the PDF viewer

Changed

Flatpak beta app ID changed from org.mozilla.Thunderbird to org.mozilla.thunderbird

Fixed

Unknown command-line arguments passed to Thunderbird did not print warning

Thunderbird could crash when creating a folder

Saved email filenames were not not always cross-platform safe

Compose progress dialog used unlocalised folder name

Clicking on a folder in the folder pane did not always open folder

Could not scroll to message bottom or view all attachments in some cases

Accounts could be listed twice after adding new account

Account Hub manual configuration was missing OAuth2 option

Microsoft Store installs did not open when clicking 'news://' link or .eml file

Folder states were not exposed to screen readers in saved search properties

Mailbox name was not announced and message count was incorrect for screen readers

POP3 could stop downloading mail until restart

Exchange servers/clients caused memory leaks by holding mutual references

Authentication could fail for some exchange accounts

'Move to New Window' option for the calendar was disabled

Calendar view had date and time axes swapped

Visual and UX improvements

Security fixes

As always, you’re encouraged to tell us what you think, ask for help, or file a bug in Bugzilla

Original source

Version 150.0, first offered to Release channel users on April 21, 2026

New

Split View just got better: You can now right-click any link and choose Open Link in Split View to open it alongside your current tab. You can also search open tabs when creating a split view and quickly reverse tab positions using the new Reverse Tabs option in the tab context menu.

Share multiple tabs in a single step. Select several tabs, right-click, and choose Copy X Links (for Windows and Linux) or choose Share Copy X Links (for MacOS). When pasted into other apps that support rich text, links include both the page title and the URL for easy reading.

You can now use Firefox's built-in PDF editor to reorder, copy, paste, delete, and export pages in a PDF.

Try out real-time, private translations in Firefox Desktop with the about:translations page. Start typing the word "translate" into the URL bar for a quick-action shortcut to the page.

Added support for the GTK emoji picker on Linux, allowing users to insert emoji using the system shortcut (typically Ctrl + .).

Firefox web apps are now available to Windows users who installed Firefox through the Microsoft Store.

The new Firefox Profile management system is now available to all users, including users on Windows 10.

Backing up a profile to a file is now available to all Windows 10 and 11 users, including those who use the new profile management system.

Firefox now ships with a new .rpm package for Linux users on Red Hat, Fedora, openSUSE, and other RPM-based distributions.

Firefox now prompts you to enable location access in Windows settings when granting a website permission to use your location, if geolocation hasn't already been allowed. This behavior, previously limited to some Windows 11 versions, now applies to all supported Windows versions.

The built-in VPN is now available for users in Canada. Note: This feature is not available in enterprise environments.
Currently available in: Canada, France, Germany, United Kingdom, United States
This feature is part of a progressive roll out.

Fixed

Fixed an issue on macOS where, when macOS Lockdown mode is enabled, emoji characters are not displayed in web content.

Various security fixes.

Changed

If you prefer creating tab groups from the context menu, you can now turn off drag-and-drop group creation in Settings > Tabs > Drag tabs to create tab groups.

Enterprise

You can find information about policy updates and enterprise-specific bug fixes in the Firefox for Enterprise 150 Release Notes.

Developer

Developer Information

A new element-specific section has been added to the pseudo-class toggle panel including a toggle for the :open pseudo-class, which is only available for elements that have an open state like elements. The existing toggle for the :visited pseudo-class was also moved there, as it only applies to and elements. (Learn More)

The Document.caretPositionFromPoint() method now only returns a position in a shadow DOM if its ShadowRoot is passed in the newly-added shadowRoots option.

The devtools network monitor now indicates when a connection used a certificate issued by a certificate authority not in Mozilla's Root CA Program.

Web Platform

Firefox now supports the ariaNotify API for accessibility notifications (e.g. for screen readers) as a more ergonomic and reliable alternative to ARIA live regions.

Firefox now supports media element pseudo-classes (e.g., :playing, :paused) to allow more precise styling based on media playback state.

Added support for the highlightsFromPoint() API, which allows web pages to interact with CSS Highlights by returning all Highlights at a given point.

Firefox now supports light-dark() on images, just like on colors, which is very useful for supporting dark mode on websites.

The color-mix() function previously accepted only two color values. This limitation has now been removed, allowing the function to accept an arbitrary number of colors.

Added support for a new auto value on the sizes attribute for lazy-loaded image elements with multiple images defined via srcset. This allows the browser to automatically select the right image based on the layout width of the image element. (Learn More)

Unresolved

Users with Bitdefender security software installed may experience problems loading websites, particularly Facebook.com. We are working on a workaround, but as a temporary mitigation, disabling Bitdefender or turning off its traffic filtering features may resolve the issue.

Community Contributions

With the release of Firefox 150, we are pleased to welcome the developers who contributed their first code change to Firefox in this release, 22 of whom were brand new volunteers! Please join us in thanking each of these diligent and enthusiastic individuals, and take a look at their contributions:

Akeldama: 1718781
Alex Reisner: 2005628
amar.p.t.1397: 2003168
Anshul Malik: 1561441, 1814459, 2018447, 2018843, 2019010
baris: 2008127
Ben: 1967026
Chad Gratts: 2003111
Elliott Ashby: 1674654
geppy: 1767617
Giedrius Visokinskas [:gvisokinskas]: 1910291
Jocsan: 2016933
Justin Peter: 1971538, 2010486, 2018840, 2018842
karan68: 1998004
Knot False: 1861645
Liam Wachter: 2018739
Michael Lynch: 2023046
Mohammed Abdullah: 1942439
Nathan Johnson [:narjoDev]: 1895394
Pushkar Singh: 2003191
Sally Frye: 2003170
Thien Pham: 2001134
tushar sariya: 928224, 1939501, 1975962

Original source

Version 149.0.2, first offered to Release channel users on April 7, 2026

Fixed

• Various security fixes.
• Fixed an issue where certain parts of web pages, such as drop-down menus and specific styles, did not appear correctly when printing. (Bug 2026109)
• Fixed an issue where some website error pages displayed generic connection messages instead of the specific error code and description provided by the server. (Bug 2023800)
• Fixed a crash that occurred when using certain security keys or WebAuthn features for two-factor authentication. (Bug 2026688)
• Fixed an issue on Linux where the browser toolbar could become unresponsive to mouse clicks after dragging a tab when using Wayland. (Bug 2022238)
• Fixed a layout issue where text inside certain graphics (SVG) appeared shifted or misaligned from its intended position. (Bug 2024647)
• Fixed an issue where the "Send to device" option failed to work when used from the Open Tabs section in Firefox View. (Bug 2023201)

Enterprise

• Introduced a new enterprise policy that allows administrators to directly manage and control AI-related features within Firefox. (Bug 2019983)
• Fixed an issue where enterprise policies for the browser homepage and start page were not being applied correctly. (Bug 2027888)
• Introduced a new enterprise policy that allows administrators to prevent the built-in VPN and IP protection features from being available to users. (Bug 2022365)

Reference link to 149.0 release notes.

Original source