Firefox 125 for developers
This article provides information about the changes in Firefox 125 that affect developers. Firefox 125 was released on April 16, 2024.
Changes for web developers
HTML
No notable changes.
CSS
- The
align-content
property has been updated to work withdisplay: block;
layouts. This brings all the layout positions fromflex
andgrid
toblock
, enabling developers to align block-level elements without converting their container to aflex
orgrid
container. (Firefox bug 1882853). - The CSS property
transform-box
now supports the valuescontent-box
andstroke-box
. For the reference box, thecontent-box
value uses the content box and thestroke-box
value uses the stroke bounding box that contains an SVG's shape (Firefox bug 1868374). - The
content-visibility
CSS property valueauto
is now enabled by default. This allows content to skip rendering if it is not relevant to the user. (Firefox bug 1874874).
JavaScript
Intl.Segmenter
is now supported, allowing developers to perform locale-sensitive text segmentation of a string. This enables, for example, splitting a string into words in languages that don't use spaces to separate them:Intl.Segmenter("ja-JP", { granularity: "word" })
. You can also split strings into graphemes or sentences. (Firefox bug 1423593, Firefox bug 1883914.)
APIs
-
The Popover API is now fully supported, allowing the creation of top level "popover" UI elements that might be used for action menus, custom "toast" notifications, form element suggestions, content pickers, and so on. The popover and its triggering button/input can be created using either HTML attributes or JavaScript, and styled using CSS.
The following Web APIs are implemented:
HTMLButtonElement
propertiespopoverTargetElement
andpopoverTargetAction
.HTMLInputElement
propertiespopoverTargetElement
andpopoverTargetAction
.HTMLElement
propertypopover
,hidePopover()
,showPopover()
, andtogglePopover()
methods, andbeforetoggle
andtoggle_event
events (of typeToggleEvent
).
The following CSS pseudo class and element are now supported for use with popovers:
:popover-open
::backdrop
has been extended to support popovers
The following HTML global attributes are supported:
-
The
RTCIceTransport
propertiesstate
andgatheringState
, and their associated eventsstatechange
andgatheringstatechange
, are now supported, along with theRTCDtlsTransport.iceTransport
property (which returns the underlyingRTCIceTransport
for aRTCDtlsTransport
). These allow much finer-grained monitoring than provided by theRTCPeerConnection
propertiesiceGatheringState
andconnectionState
. (Firefox bug 1811912) -
Element.ariaBrailleLabel
andElement.ariaBrailleRoleDescription
are now supported, respectively reflecting the global ARIA HTML attributesaria-braillelabel
andaria-brailleroledescription
. (Firefox bug 1861201). -
Added support to allow web applications to gracefully recover if a canvas temporarily loses its 2D context, which might happen if the canvas is running hardware-accelerated on a GPU, and its driver crashes (Firefox bug 1887729). Here are some additional details on the events for lost and restored canvas contexts:
- Applications can monitor for
contextlost
andcontextrestored
events, which are fired on atHTMLCanvasElement
when the context is lost and recovered, respectively, and can also check the context usingCanvasRenderingContext2D.isContextLost()
. - After emitting
contextlost
, a browser will try and restart the lost context, by default, but code can prevent this by cancelling the event. - Offscreen canvases can be monitored in the same way, but using
OffScreenCanvas
eventscontextlost
andcontextrestored
, along withOffscreenCanvasRenderingContext2D.isContextLost()
.
- Applications can monitor for
-
Added support for the
shadowrootclonable
attribute of the<template>
element, and theshadowRootClonable
property of theHTMLTemplateElement
interface that reflects it. These set theclonable
property of aShadowRoot
that has been created declaratively using the<template>
element. (Firefox bug 1880188). -
The
readText()
method of theClipboard
interface is now supported for asynchronously reading text from the system clipboard. When reading clipboard data that is not provided by the same-origin page, a paste context menu will appear for the user to confirm. (Firefox bug 1877400).
Media, WebRTC, and Web Audio
- The AV1 codec is now supported for Encrypted Media Extensions, enabling higher-quality playback from video streaming providers. (Firefox bug 1601817).
Removals
- The
SVGAElement.text
property has been removed. ThetextContent
property (inherited fromNode
) is broadly supported and should be used instead. (Firefox bug 1880689).
WebAssembly
- Support has been added for Wasm modules to use multiple independent linear memories. Multiple memories enable more efficient interoperability between modules and better polyfills for upcoming Wasm standards. They can be used, for example, to create separate memory for internal and shared data, ephemeral and persisted data, or data that needs to be shared between threads. The memory can be created in JavaScript and imported into the Wasm module, or created in the Wasm module and exported. Each new linear memory in a Wasm instance is given a sequential index, starting from zero. WebAssembly memory instructions use the index to reference the memory on which they are operating, defaulting to the first memory defined if no index is specified. For more information, see WebAssembly Memory in Understanding WebAssembly text format. (Firefox bug 1860816).
WebDriver conformance (WebDriver BiDi, Marionette)
General
- Added support for the "userAgent" capability which identifies the default User-Agent value of the endpoint node (Firefox bug 1885495).
WebDriver BiDi
- Added support for the input.setFiles command which allows to set or update the files for
<input>
elements withtype="file"
(Firefox bug 1855040). - Added support for the storage.deleteCookies command to delete cookies (Firefox bug 1854581).
- Added support for "userContext" as a field of the "partition" argument for cookie commands (Firefox bug 1875255).
- Fixed an issue where storage.getCookies would not retrieve all expected cookies for a given "sourceOrigin" (Firefox bug 1884647).
- Fixed an issue where recommended preferences would not be applied if only WebDriver BiDi as remote protocol, which means CDP is disabled, was enabled (Firefox bug 1882748).
- Fixed an issue where creating and switching to a new tab would not wait for the
visibilityState
to be updated (Firefox bug 1877469).
Changes for add-on developers
- The content of the
proxy.ProxyInfo
propertyproxyAuthorization
is now passed to theProxy-Authorization
request header sent to HTTP proxies (in addition to the existing support for HTTPS proxies) as part of a CONNECT request (Firefox bug 1794464).
Experimental web features
These features are shipping in Firefox 125 but only in developer releases or behind a preference. To try these out, you can search for the related preference on the about:config
page to see if they're enabled or disabled. To learn more about these features, see the Experimental features page.
-
CSS
transition-behavior
:layout.css.transition-behavior.enabled
.The
transition-behavior
property is enabled by default in the Nightly release. Authors can use this property to control whether to apply CSS transitions to properties with a discrete animation type (Firefox bug 1882408, Firefox bug 1805727). -
UA styles for
<h1>
nested into sectioning elements:layout.css.h1-in-section-ua-styles.enabled
.The
<h1>
heading doesn't decrease in font size now when nested within sectioning elements<article>
,<aside>
,<nav>
, and<section>
. The UA styles for<h1>
nested within sectioning elements are no longer relevant since the outline algorithm has been removed from the HTML specification. (Firefox bug 1883896).Note: The preference for this feature works in reverse: it's set to
false
in the Nightly build, which removes the UA styling for headings nested in sectioning elements. It's set totrue
in all other channels, which retains the existing UA styling for the nested headings.
Older versions
- Firefox 124 for developers
- Firefox 123 for developers
- Firefox 122 for developers
- Firefox 121 for developers
- Firefox 120 for developers
- Firefox 119 for developers
- Firefox 118 for developers
- Firefox 117 for developers
- Firefox 116 for developers
- Firefox 115 for developers
- Firefox 114 for developers
- Firefox 113 for developers
- Firefox 112 for developers
- Firefox 111 for developers
- Firefox 110 for developers
- Firefox 109 for developers
- Firefox 108 for developers
- Firefox 107 for developers
- Firefox 106 for developers
- Firefox 105 for developers
- Firefox 104 for developers
- Firefox 103 for developers
- Firefox 102 for developers
- Firefox 101 for developers
- Firefox 100 for developers
- Firefox 99 for developers
- Firefox 98 for developers
- Firefox 97 for developers
- Firefox 96 for developers
- Firefox 95 for developers
- Firefox 94 for developers