Mozilla Release Notes

Version 152.0.4, first offered to Release channel users on June 30, 2026

New

Smart Window includes several enhancements:

• You can now ask it to close your tabs, with a confirmation step when needed and the option to undo afterward. (Bug 2040769)
• Browsing history results now appear with images. (Bug 2038069)
• When you give feedback on a response, you can now choose from common reasons and preview exactly what will be shared before submitting. (Bug 2033002)

This feature is part of a progressive roll out.

What is a progressive roll out?

Certain new Firefox features are released gradually. This means some users will see the feature before everyone does. This approach helps to get early feedback to catch bugs and improve behavior quickly, meaning more Firefox users overall have a better experience.

Fixed

Fixed copy, paste, undo, redo, and similar keyboard shortcuts not working inside macOS system dialogs such as the Save and Open panels. (Bug 2040851, Bug 2040844)

Fixed the Manage Cookies and Site Data dialog opening with an empty list when opened from the Settings search results. (Bug 2041077)

Fixed keyboard focus landing in the wrong place after following an in-page link, so pressing Tab continues from the link's position as expected. (Bug 2049307)

Various security fixes.

Reference link to 152.0.3 release notes.

Version 152.0.2, first offered to Release channel users on June 23, 2026

Fixed

Fixed some Settings section headings showing placeholder text instead of the translated name in certain languages. (Bug 2047983)

Fixed New Tab content not matching the browser's display language after it was changed. (Bug 2046945)

Fixed a regression that could break playback of some MP4 video files. (Bug 2047467)

Fixed a performance regression that could slow down sites performing many encryption and decryption operations at once, such as Proton Drive. (Bug 2046401)

Reference link to 152.0.1 release notes.

Unresolved

Some users with a language pack installed may experience high memory usage and an unresponsive browser on startup. (Bug 2049845)

Version 152.0, first offered to Release channel users on June 16, 2026

New

• Firefox Settings features a brand-new look with streamlined organization, clearer groupings, and improved navigation for easier customization.
• In Private Browsing windows, you can now temporarily disable tracker blocking for a tab if it's causing a site to break. When you reload a page where trackers were blocked, Firefox shows a message offering to reload without the stricter protections. All other tracking protections stay active.
• You can now mute your browser from the address bar: type "mute" (or "shush" or "sssh") and use the address bar quick action to silence every tab currently playing sound across all Firefox windows.
• Improved support for more advanced cursor movement commands, including those relating to paragraph boundaries, on macOS.
• On Windows and Linux, you can now copy links via the tab context menu by right-clicking a tab and selecting Share > Copy Link, making it easy to copy a link without switching to the tab first. When multiple tabs are selected, you can copy all selected links at once. Windows users still retain access to Microsoft sharing options from the Share menu.
• A "Send tab" toolbar button is now available which can be added via More Tools > Customize Toolbar.
• The following languages are now available for Translations: Basque, Galician.
• Firefox builds in Croatian, English (UK), Georgian, Persian, Slovenian, Tajik, Tamil, Tibetan, Turkish, Welsh, and Xhosa now come with a built-in dictionary for the Firefox spellchecker.

Firefox Labs

• Firefox now offers experimental support for the new JPEG XL image format, which generally provides better compression than WebP, JPEG, PNG, and GIF and is designed to supersede them. You can enable it from the Firefox Labs panel in Settings.

Fixed

• Fixed an issue where the Paste option could be missing from context menus when editing content on sites such as Squarespace, LinkedIn, and eBay.
• Improved dragging images from Firefox to the desktop or Finder on macOS — images now save reliably and land where you drop them.
• In multiple monitor situations, the About Firefox window now more reliably opens on the display with the most recently used Firefox window.
• Fixed arrow-key text navigation and word selection commands that moved in the wrong direction in right-to-left text on macOS and Linux.
• Various security fixes.

Changed

• Site zooming via keyboard or mouse now offers more zoom levels in smaller increments than before.
• When a PDF or other file that Firefox opens directly finishes downloading, it now opens in a background tab if you've switched tabs or closed the original page.
• The Tabs from Other Devices panel in the sidebar now lets you open tabs in a new tab or a new container tab from the context menu.

Developer

• Developer Tools now have an option in the Settings panel to toggle the display of comment nodes in the Inspector.

Web Platform

• Web Notifications can now have action buttons via the actions option. They appear as buttons below the notification text or in the Options list on macOS.
• The field-sizing property is now available, allowing form controls to adjust in size to fit their contents.
• Firefox now supports the WebAuthn Related Origin Request feature, which simplifies login flows by making Passkeys usable from multiple domains.
• The Pointer Lock API now supports the unadjustedMovement option, allowing sites to receive raw mouse-movement data unaffected by OS-level acceleration.

Community Contributions

With the release of Firefox 152, we are pleased to welcome the developers who contributed their first code change to Firefox in this release, 25 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: :23rd: 1812100, :Vincent: 2033780, Akeem Omosanya: 2031351, 2035252, Amin Amir: 2031353, 2031355, 2031599, 2033820, Amine Zroual: 1392125, Andrew Gaul: 2032275, Andy [:rgbcmy]: 1611643, Eugeniusz Lewandowski: 1650944, 2036580, Helmut Januschka: 2006340, Jak: 2030070, JIANG Zhirui: 2036199, liz: 1875083, 2008119, 2011485, Mubashshir: 1803078, Noah Peterson: 1829401, Rahman Mahmutović [:r_m]: 1717176, Sahaj: 2031015, Takeru Mitsumori: 2038948, Tim Elliott: 2031507, tom.passarelli: 2031328, Tymur Boiko: 2035749, 2036839, 2039309, Vignesh B [:vsr-b]: 1895393, 1966844, vinitjangir: 790194, 2000360, vyofgod: 2031349, 2031356, 2031357, 2031371, 2031377, 2031381.

What’s New

SecurityDevices enabled in enterprise policies

One-click account setup for Thundermail accounts

Changed

Use 'Add' instead of 'New' for account, calendar, address book creation buttons

GMail OAuth updated to use PKCE

Hostname of mail server is also checked when detecting address books and calendars

Updated about:rights to replace local with hosted url

'Hide completed tasks' now also hides cancelled tasks

Fixed

New mail alerts appeared on wrong monitor in three-monitor setup

Spam messages triggered new mail notifications before being moved to Spam folder

Filtered IMAP or NNTP subscriptions were lost after closing Subscribe dialog

'Download Headers' dialog for newsgroups failed to open

Messages nested deeper than 255 levels disappeared from threading view

Performing Delete followed by Undo on thread parent message could corrupt view

Single messages still appeared collapsible after thread members were deleted

Updated threads remained misordered until folder refresh or resort

Non-threaded subject sorting separated 'RE:' replies from original messages

BCC recipients were included in signed email headers

Performance issue when decrypting encrypted messages

Filter search on Body missed draft messages containing German umlauts

Thunderbird could crash during local message search

Blocked file warning showed without 'Unblock File' button in compose window

Forwarding/Redirecting Exchange messages failed with NS_ERROR_OUT_OF_MEMORY

Compose window closed early and send progress dialog hung after NNTP failure

Compose window stayed open after sending when mailnews.sendInBackground set

Microsoft OAuth2 failed when HTTPS localhost redirect was not intercepted

Pasting contact photos stopped working when photo button had focus

Filter dialog lacked focus ring and had poorly distinguishable buttons

Subfolder kept stale accessibility unread count after unread messages were deleted

'Edit as New Message' and inline 'Forward' not possible with PGP-signed messages

Various MIME improvements

EWS messages could go missing from folder view

IMAP "Show only subscribed folders" could not be changed without restart

Unable to delete more than 1000 messages at a time on Microsoft 365

EWS folders in Trash were moved to Trash again instead of being hard deleted

IMAP notifications repeated for emails read on another device after sleep wake

POP3 deadlocked when server went silent without closing socket

Calendar acceptance no longer distinguished between single occurrence and series

Transparent popups on macOS made calendar event editing difficult

Duplicate attendees were added to invitations instead of being filtered out

Task percentage complete was not preserved separately from status in tooltips

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

Version 151.0.4, first offered to Release channel users on June 9, 2026

Fixed

Fixed an issue on Windows where Firefox could become unresponsive when using the back and forward buttons. (Bug 2039866)

Fixed an issue where Firefox could fall back to software rendering on some older GPUs, reducing graphics performance. (Bug 2043249)

Fixed a crash on Windows that could occur when Firefox interacted with accessibility services. (Bug 204330)

Fixed an issue where some text input fields could incorrectly show a resize handle. (Bug 2044051)

Reference link to 151.0.3 release notes.

Version 151.0.2, first offered to Release channel users on May 26, 2026

Fixed

Fixed an issue on macOS where smart cards and security keys could fail to load certificates automatically. (Bug 2041208)
Fixed an issue where adding another tab to an existing Split View could unexpectedly close it. (Bug 2039795)
Fixed an issue where Split View would close instead of switching tabs when using the "Switch to Tab" option from the address bar. (Bug 2039787)
Fixed a crash on Windows that occurred when using the Sogou input method to type Simplified Chinese. (Bug 2039203)
Fixed an issue where Firefox stopped caching new content once the disk cache was full, causing pages and resources to be re-downloaded from the network on every visit. (Bug 2031577)
Fixed an issue where some websites could render incorrectly or fail to load when they used JavaScript to insert WebKit-specific style rules. (Bug 2040693)
Fixed an issue where clicking and selecting text in some input fields and text areas did not work on pages that styled them with certain CSS rules. (Bug 2039504)
Fixed an issue where the up and down buttons on number input fields could overlap and hide the value when sites sized the field to fit its contents. (Bug 2039315)
Fixed an issue where sorting strings that include numbers could produce an incorrect order on some websites and web applications. (Bug 2027078)
Fixed an issue where dropdown menus would not open for <select> elements created inside an iframe and then moved into the parent page. (Bug 2041720)

Reference link to 151.0.1 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

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