Firefox Intelligence
A plain-English digest rebuilt from the latest official Stable, Beta, and Nightly release notes. Every visible card links back to the Mozilla source used for it.
Engine
Platform and engine-level work landing in Gecko — the parts of Firefox most people never see, explained plainly.
Starting with Firefox 154, Firefox Nightly now supports the alpha() CSS function. This is a relative color function that can be used to modify just the alpha component of a given color. Bug 2047437.
Published for Firefox 155.0a1 (nightly) in Mozilla's web-platform notes. This is part of the current Gecko and web-platform picture across active channels.
Starting with Firefox 153, Firefox Nightly ships an experimental implementation of the link-parameters property by Tyler Thrailkill. Bug 2046153.
Published for Firefox 155.0a1 (nightly) in Mozilla's web-platform notes. This is part of the current Gecko and web-platform picture across active channels.
Starting with Firefox 153, Firefox Nightly now supports two new keywords closest-corner and farthest-corner for the radial size in the circle() and ellipse() functions. Bug 2045278.
Published for Firefox 155.0a1 (nightly) in Mozilla's web-platform notes. This is part of the current Gecko and web-platform picture across active channels.
Developer Information.
Published for Firefox 155.0a1 (nightly) in Mozilla's developer notes. This is part of the current Gecko and web-platform picture across active channels.
Added a time picker user interface to <input type="time"> and <input type="datetime-local">, making selecting a time more accessible and intuitive.
Published for Firefox 154.0b4 (beta) in Mozilla's web-platform notes. This is part of the current Gecko and web-platform picture across active channels.
Firefox now supports the sibling-index() and sibling-count() CSS functions. These functions allow an element to be styled with calculations that use its index among its siblings and its total count of siblings (including itself), respectively.
Published for Firefox 154.0b4 (beta) in Mozilla's web-platform notes. This is part of the current Gecko and web-platform picture across active channels.
Firefox now supports the Iterator.prototype.join method that allows joining an iterator into a string, similar to Array.prototype.join.
Published for Firefox 154.0b4 (beta) in Mozilla's web-platform notes. This is part of the current Gecko and web-platform picture across active channels.
Added support for the No-Vary-Search HTTP response header for the HTTP disk cache. Servers can now declare which URL query parameters are irrelevant to the response, allowing Firefox to reuse cached resources across parameter variations and improving cache hit rates.
Published for Firefox 154.0b4 (beta) in Mozilla's web-platform notes. This is part of the current Gecko and web-platform picture across active channels.
Firefox now supports new Iterator.prototype.chunks and Iterator.prototype.windows methods that allow consuming an iterator as either overlapping or non-overlapping subsequences of configurable size.
Published for Firefox 154.0b4 (beta) in Mozilla's web-platform notes. This is part of the current Gecko and web-platform picture across active channels.
Firefox now supports the text-box-trim and text-box-edge CSS properties, and the associated text-box shorthand. These properties allow you to control the leading space above and below text, enabling simpler and consistent vertical spacing and alignment.
Published for Firefox 154.0b4 (beta) in Mozilla's web-platform notes. This is part of the current Gecko and web-platform picture across active channels.
The RTCIceTransport.getSelectedCandidatePair() method and selectedcandidatepairchange event are now supported for getting the current RTCIceCandidatePair for the transport. ( Firefox bug 2019332 ).
Published for Firefox 154.0b4 (beta) in Mozilla's web-platform notes. This is part of the current Gecko and web-platform picture across active channels.
The error event is now fired on RTCDtlsTransport to report DTLS and fingerprinting errors. ( Firefox bug 1805447 ).
Published for Firefox 154.0b4 (beta) in Mozilla's web-platform notes. This is part of the current Gecko and web-platform picture across active channels.
The JSON Viewer now shows a breadcrumb path at the bottom for the selected entry.
Published for Firefox 154.0b4 (beta) in Mozilla's developer notes. This is part of the current Gecko and web-platform picture across active channels.
Firefox now supports Iterator.prototype.includes() , allowing developers to check whether an iterator contains a given value without first converting it to an array.
Published for Firefox 154.0b4 (beta) in Mozilla's developer notes. This is part of the current Gecko and web-platform picture across active channels.
Text selected in PDFs is now highlighted clearly like in normal web pages. The selection color also follows OS settings like high-contrast mode.
Published for Firefox 154.0b4 (beta) in Mozilla's changed notes. This is part of the current Gecko and web-platform picture across active channels.
Video seeking is now significantly faster on macOS, making scrubbing and jumping to a point in a video much more responsive.
Published for Firefox 154.0b4 (beta) in Mozilla's changed notes. This is part of the current Gecko and web-platform picture across active channels.
In Firefox for Android , Bookmarks Search now shows up to 75 results per query, making it easier to find your bookmarks without refining your search.
Published for Firefox 154.0b4 (beta) in Mozilla's changed notes. This is part of the current Gecko and web-platform picture across active channels.
Firefox View is moving out of the toolbar by default for new profiles and profiles where it hasn’t been used recently. You can still open it from List all tabs > View all tabs , or add it back from the Customize toolbar menu.
Published for Firefox 154.0b4 (beta) in Mozilla's changed notes. This is part of the current Gecko and web-platform picture across active channels.
Nightly
What changed in the daily build overnight. The earliest, rawest signal of where Firefox is heading.
Starting with Firefox 154, We’re testing a simpler tab context menu in Firefox Labs. Turn it on in Settings > Firefox Labs > Streamline tab menu and tell us what you think on Mozilla Connect . Bug 2031718.
First seen in Firefox 155.0a1 Nightly. Nightly changes are experimental and may be adjusted or reverted before reaching Beta.
Starting with Firefox 154, Firefox Nightly now supports QUIC version 2 ( RFC 9369 ) for HTTP/3 connections. Firefox offers both QUIC v1 and v2 using compatible version negotiation ( RFC 9368 ). The server selects which version is used, so connections upgrade to QUIC v2 when the server chooses it and remain on QUIC v1 otherwise. Bug 2040450.
First seen in Firefox 155.0a1 Nightly. Nightly changes are experimental and may be adjusted or reverted before reaching Beta.
Experiments
Features hidden behind flags and origin trials — things you can try today, long before they reach everyone.
Starting with Firefox 154, We’re testing a simpler tab context menu in Firefox Labs. Turn it on in Settings > Firefox Labs > Streamline tab menu and tell us what you think on Mozilla Connect . Bug 2031718.
Published by Mozilla for Firefox 155.0a1 (nightly) in the new release-note category.
Starting with Firefox 154, Firefox Nightly now supports QUIC version 2 ( RFC 9369 ) for HTTP/3 connections. Firefox offers both QUIC v1 and v2 using compatible version negotiation ( RFC 9368 ). The server selects which version is used, so connections upgrade to QUIC v2 when the server chooses it and remain on QUIC v1 otherwise. Bug 2040450.
Published by Mozilla for Firefox 155.0a1 (nightly) in the new release-note category.
Patches
Notable fixes and patches moving through review — the bugs being squashed before they reach your build.
Addressed a startup crash on Windows that could occur after updating Firefox, when some of the application's internal files could not be loaded. Firefox should now start in these cases, although parts of the interface may not display correctly until a further update completes ( Bug 2056926 ).
Published by Mozilla for Firefox 153.0.1 (stable) in the fixed release-note category.
Fixed audio playing silently on some music and audio streaming sites after pausing and resuming playback ( Bug 2053586 ).
Published by Mozilla for Firefox 153.0.1 (stable) in the fixed release-note category.
Fixed the New Tab page background flashing a few seconds after the page loaded when a custom wallpaper was in use ( Bug 2056650 ).
Published by Mozilla for Firefox 153.0.1 (stable) in the fixed release-note category.
Fixed a crash that could occur when a page loaded a frame using a javascript: address ( Bug 2054485 ).
Published by Mozilla for Firefox 153.0.1 (stable) in the fixed release-note category.
Fixed a crash that could occur while typing text in an editable area of a page ( Bug 2053867 ).
Published by Mozilla for Firefox 153.0.1 (stable) in the fixed release-note category.
Fixed a search engine you had already installed yourself being labeled as "New" when Firefox later started offering the same engine ( Bug 2053710 ).
Published by Mozilla for Firefox 153.0.1 (stable) in the fixed release-note category.
Improved pointer lock, used by games and other immersive web content, so that the mouse pointer is less likely to escape the Firefox window ( Bug 1255338 , Bug 2040628 ).
Published by Mozilla for Firefox 153.0.1 (stable) in the fixed release-note category.
Fixed an issue in the Inspector's Rules view where pseudo-elements could only be expanded once per selected element ( Bug 2054525 ).
Published by Mozilla for Firefox 153.0.1 (stable) in the fixed release-note category.
Trust
Advisories, hardening, and privacy work. The changes that quietly keep your browsing yours.
Various security fixes .
Published by Mozilla for Firefox 153.0 (stable) in the security release-note category.
Speed
Speed, memory, and responsiveness wins — measured improvements to how Firefox actually feels.
Video seeking is now significantly faster on macOS, making scrubbing and jumping to a point in a video much more responsive.
Performance-related note published by Mozilla for Firefox 154.0b4 (beta).
Addressed a startup crash on Windows that could occur after updating Firefox, when some of the application's internal files could not be loaded. Firefox should now start in these cases, although parts of the interface may not display correctly until a further update completes ( Bug 2056926 ).
Performance-related note published by Mozilla for Firefox 153.0.1 (stable).
Some Windows users may experience a crash on startup after updating, caused by an incomplete update leaving the Firefox installation in an inconsistent state ( Bug 1681745 ). If you are affected, downloading Firefox from firefox.com and installing it over your existing installation will repair it. Your bookmarks, passwords and other data are stored separately and will not be affected.
Performance-related note published by Mozilla for Firefox 153.0.1 (stable).
Some Windows users may experience a crash on startup after updating, caused by an incomplete update leaving the Firefox installation in an inconsistent state ( Bug 1681745 ). If you are affected, downloading Firefox from firefox.com and installing it over your existing installation will repair it. Your bookmarks, passwords and other data are stored separately and will not be affected.
Performance-related note published by Mozilla for Firefox 153.0 (stable).
The newly added Error.stackTraceLimit property allows to set the maximal depth of the captured JavaScript error stack as a performance optimization.
Performance-related note published by Mozilla for Firefox 153.0 (stable).
The Error.stackTraceLimit static data property is supported for setting or getting the maximum number of stack frames captured in an error stack trace. Setting the value smaller than the default can improve performance. ( Firefox bug 2037856 ).
Performance-related note published by Mozilla for Firefox 153.0 (stable).
The decodingInfo() and encodingInfo() methods of the MediaCapabilities interface now accept the "webrtc" configuration type. This allows a site to query whether a given audio or video configuration can be decoded or encoded using WebRTC, and whether doing so will be smooth, power efficient, or both. Support for the non-standard transmission type, which was used as an alias for webrtc , is removed. ( Firefox bug 2037610 and Firefox bug 2032075 ).
Performance-related note published by Mozilla for Firefox 153.0 (stable).
Ecosystem
Beyond the browser: the organisation, the open web mission, and the projects shaping what comes next.
You can find information about policy updates and enterprise-specific bug fixes in the Firefox for Enterprise 153 Release Notes .
Published by Mozilla for Firefox 153.0 (stable) in the enterprise release-note category.
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