Firefox 129 for developers
This article provides information about the changes in Firefox 129 that affect developers. Firefox 129 was released on August 6, 2024.
Changes for web developers
CSS
- The @starting-style CSS at-rule is supported. This lets you define starting values for properties set on an element that you want to transition from when the element receives its first style update. Currently animating from
display: none;
is not supported (Firefox bug 1834876 and Firefox bug 1834877). - The
transition-behavior
CSS property is supported. This lets you specify if discrete properties, such asdisplay
andoverlay
, can be transitioned by setting the value toallow-discrete
. (Firefox bug 1901645). -webkit-font-feature-settings
has been implemented as an alias of the standardfont-feature-settings
property (Firefox bug 1595620).
JavaScript
Float16Array
typed arrays are now supported, along withDataView.prototype.getFloat16()
andDataView.prototype.setFloat16()
for reading and settingFloat16Array
values from aDataView
, and theMath.f16round()
static method, which can be used to round numbers to 16 bits. The new type is useful for sharing data with a GPU, in particular for use cases where it makes sense to trade off precision for memory consumption. (Firefox bug 1903329.)- Regular expressions can now use the same name for named capturing groups in different disjunction alternatives. This is allowed because only one alternative in a disjunction will match, so a name declared in several alternatives can only reference one captured group. The names must still be unique within a particular alternative, and across the rest of the pattern. (Firefox bug 1903288.)
HTTP
- HTTPS DNS records can now be resolved using the operating system's DNS resolver on Windows 11, Linux, and Android 10+. This ensures that DNS over HTTPS (DoH) will be used if a user has enabled it on the device, even if it is not enabled in the browser. This feature allows the use of HTTP/3 without needing to use the
Alt-Svc
header and enables automatic upgrade of HTTP requests to HTTPS when the HTTPS DNS record is present. Most importantly, it now allows the use of Encrypted Client Hello (ECH) privacy feature even when DoH is only enabled on the device, not in the browser. (Firefox bug 1906239).
APIs
- The deprecated
textInput
event is now supported, enabling web apps that use legacy libraries or frameworks that rely on these events. Thebeforeinput
event supersedestextInput
, and should always be used by new applications. (Firefox bug 1901923.) - The default
.toJSON()
methodsGeolocationCoordinates.toJSON()
andGeolocationPosition.toJSON()
are now supported, enabling serialization ofGeolocationCoordinates
andGeolocationPosition
objects withJSON.stringify()
(Firefox bug 1890706). CSSPageDescriptors
is now supported, and is used as the type forCSSPageRule.style
instead ofCSSStyleDeclaration
— matching the current specification. This ensures thatCSSPageDescriptors
only exposes the@page
related properties, rather than all properties, and also resolves an issue where setting the pagesize
in a CSS@page
at-rule was not reflected inCSSPageRule.style
. (Firefox bug 1890842, Firefox bug 1867106.)MediaCapabilities.decodingInfo()
can now get decoding information for a particular encrypted media configuration as well unencrypted media, allowing applications to tell ahead of time if the configuration is supported, and whether it will play the content smoothly and be power efficient. Changes include a new propertykeySystemConfiguration
on the method'sconfiguration
argument that defines the properties of the key system used to encrypt the media, and a newkeySystemAccess
property on the returned object, which is aMediaKeySystemAccess
object that can be used to create keys and decode the content for playback. (Firefox bug 1898344).- Firefox now fires events for a synchronous
XMLHttpRequest
before firing the events for any ongoing asynchronousXMLHttpRequest
. This fixes a long-standing behavioral difference with other browsers. Note that while this should fix some sites, it may also cause degraded performance on sites that expect the old "non-blocking" behaviour for a synchronousXMLHttpRequest
. Please file a bug if your website should have been fixed by this change but still appears to have related issues. (Firefox bug 697151.) - The Ed25519 digital signature algorithm is supported by the Web Crypto API, and can be used in the
SubtleCrypto
methods:sign()
,verify()
,generateKey()
,importKey()
andexportKey()
(Firefox bug 1804788). - The
contentType
andresponseStatus
properties of thePerformanceResourceTiming
interface are now supported, indicating the content type of the fetched resource and the HTTP response status code returned when fetching the resource, respectively. (Firefox bug 1800443, Firefox bug 1796785.) - The
RTCDTMFSender.canInsertDTMF
property is now supported. It enables you to check whether a WebRTC sender can insert DTMF tones into the outgoing connection. If supported, you can insert DTMF tones by usingRTCDTMFSender.insertDTMF()
. (Firefox bug 1623193).
Removals
- The
Navigator.vibrate()
method has been removed (Firefox bug 1653318, Firefox bug 1900037).
WebDriver conformance (WebDriver BiDi, Marionette)
Removals
- By default CDP (Chrome DevTools Protocol) is now disabled. It can be re-enabled via the
remote.active-protocols
preference. You can learn more about this on the following blog post. (Firefox bug 1882089)
WebDriver BiDi
- Added support for the
network.setCacheBehavior
command, which allows to configure the browser to bypass the network cache either globally or for a set of top level browsing contexts. (Firefox bug 1901032 and Firefox bug 1906100) - Added support for prompts of type
beforeUnload
which can now be handled in the same way as other user prompts. (Firefox bug 1824220) - We now support all arguments for the
network.provideResponse
command when used in thebeforeRequestSent
phase, such as thebody
parameter which allows to return mock responses. (Firefox bug 1853882) - The
browsingContext.userPromptOpened
now includes thehandler
field which contains the user prompt handler configured for the prompt which triggered the event. (Firefox bug 1904822) - The
BrowsingContextInfo
type will now provide anoriginalOpener
field which is the context id of the "opener" browsing context. This will be set for instance if the new context was created by using a link (even withrel=noopener
),window.open
etc. If the new browsing context has no relevant opener, the field will be set to null. (Firefox bug 1898004) - Network events (
beforeRequestSent
,responseStarted
andresponseCompleted
) are now created for requests to data URLs. In Firefox 129, only navigation requests will be listed. (Firefox bug 1805176) - We added support for the
promptUnload
argument forbrowsingContext.close
, which allows to bypass "beforeunload" prompts when closing a context via this command. (Firefox bug 1862380) - Fixed a bug in
network.continueRequest
where you could not set multiple values for the same header. (Firefox bug 1904379) - Fixed a bug for the
unhandledPromptBehavior
capability, which could not be used with BiDi only sessions. (Firefox bug 1907935) - Fixed a bug with
session.end
andbrowser.close
which would unexpectedly fail when no Marionette client was connected. (Firefox bug 1890091) - Fixed a bug with
browsingContext.navigate
which would fail to resolve if a same-document navigation started on "beforeunload". (Firefox bug 1879163) - Improved the
browser.close
command to discard all "beforeunload" prompts when closing the top-level browsing contexts. (Firefox bug 1873196) - Fixed a bug in the
browsingContext.userPromptOpened
event, which would unexpectedly miss thedefaultValue
field (Firefox bug 1859814) - Fixed an issue with the
network.responseCompleted
event during authentication flows, which was emitted too many times compared to the specifications. Only oneresponseCompleted
(orfetchError
) event is expected for the whole HTTP authentication flow. (Firefox bug 1906106) - Improved the
browser.removeUserContext
command to skip all "beforeunload" prompts. (Firefox bug 1876062)
Older versions
- Firefox 128 for developers
- Firefox 127 for developers
- Firefox 126 for developers
- Firefox 125 for developers
- 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