Experimental features in Firefox

This page lists Firefox's experimental and partially implemented features, including those for proposed or cutting-edge web platform standards, along with information on the builds in which they are present, whether or not they are activated "by default", and which preference can be used to activate or deactivate them. This allows you to test the features before they are released.

New features appear first in the Firefox Nightly build, where they are often enabled by default. They later propagate though to Firefox Developer Edition and eventually to the release build. After a feature is enabled by default in a release build, it is no longer considered experimental and should be removed from the topic.

Experimental features can be enabled or disabled using the Firefox Configuration Editor (enter about:config in the Firefox address bar) by modifying the associated preference listed below.

Note: For editors - when adding features to these tables, please try to include a link to the relevant bug or bugs using [Firefox bug <number>](https://bugzil.la/<number>).

HTML

Layout for input type="search"

Layout for input type="search" has been updated. This causes a search field to have a clear icon once someone starts typing in it, to match other browser implementations. (See Firefox bug 558594 for more details.)

Release channel Version added Enabled by default?
Nightly 81 No
Developer Edition 81 No
Beta 81 No
Release 81 No
Preference name layout.forms.input-type-search.enabled

Toggle password display

HTML password input elements (<input type="password">) include an "eye" icon that can be toggled to display or obscure the password text (Firefox bug 502258).

Release channel Version added Enabled by default?
Nightly 96 No
Developer Edition 96 No
Beta 96 No
Release 96 No
Preference name layout.forms.input-type-show-password-button.enabled

CSS

Hex boxes to display stray control characters

This feature renders control characters (Unicode category Cc) other than tab (U+0009), line feed (U+000A), form feed (U+000C), and carriage return (U+000D) as a hexbox when they are not expected. (See Firefox bug 1099557 for more details.)

Release channel Version added Enabled by default?
Nightly 43 Yes
Developer Edition 43 No
Beta 43 No
Release 43 No
Preference name layout.css.control-characters.enabled or layout.css.control-characters.visible

initial-letter property

The initial-letter CSS property is part of the CSS Inline Layout specification and allows you to specify how dropped, raised, and sunken initial letters are displayed. (See Firefox bug 1223880 for more details.)

Release channel Version added Enabled by default?
Nightly 50 No
Developer Edition 50 No
Beta 50 No
Release 50 No
Preference name layout.css.initial-letter.enabled

content-visibility: auto value

The content-visibility CSS property value auto allows content to skip rendering if it is not relevant to the user. (See Firefox bug 1798485 for more details.)

Release channel Version added Enabled by default?
Nightly 113 Yes
Developer Edition 109 No
Beta 109 No
Release 109 No
Preference name layout.css.content-visibility.enabled

Note:

  • The related contentvisibilityautostatechange event and associated ContentVisibilityAutoStateChangeEvent interface were added in version 110, and are gated by the same preference. These can be used by application code to monitor visibility changes and stop processes related to rendering the element when the user agent is skipping its contents. (See Firefox bug 1791759 for more details.)
  • The Element.checkVisibility() options object parameter now takes the property contentVisibilityAuto, which can be set true to test if the element has content-visibility: auto set and is currently skipping rendering its content (the options object also takes new values opacityProperty and visibilityProperty but these are not related to content-visibility). (See Firefox bug 1859852 for more details).

Single numbers as aspect ratio in media queries

Support for using a single <number> as a <ratio> when specifying the aspect ratio for a media query. (See Firefox bug 1565562 for more details.)

Release channel Version added Enabled by default?
Nightly 70 No
Developer Edition 70 No
Beta 70 No
Release 70 No
Preference name layout.css.aspect-ratio-number.enabled

backdrop-filter property

The backdrop-filter property applies filter effects to the area behind an element. (See Firefox bug 1178765 for more details.)

Release channel Version added Enabled by default?
Nightly 70 No
Developer Edition 70 No
Beta 70 No
Release 70 No
Preference name layout.css.backdrop-filter.enabled

Masonry grid layout

Adds support for a masonry-style layout based on grid layout where one axis has a masonry layout and the other has a normal grid layout. This allows developers to easily create gallery style layouts like on Pinterest. See Firefox bug 1607954 for more details.

Release channel Version added Enabled by default?
Nightly 77 Yes
Developer Edition 77 No
Beta 77 No
Release 77 No
Preference name layout.css.grid-template-masonry-value.enabled

fit-content() function

The fit-content() function as it applies to width and other sizing properties. This function is already well-supported for CSS Grid Layout track sizing. (See Firefox bug 1312588 for more details.)

Release channel Version added Enabled by default?
Nightly 91 No
Developer Edition 91 No
Beta 91 No
Release 91 No
Preference name layout.css.fit-content-function.enabled

Scroll-driven animations

Earlier called "scroll-linked animations", a scroll-driven animation depends on the scroll position of a scrollbar instead of time or some other dimension. The scroll-timeline-name and scroll-timeline-axis properties (and the scroll-timeline shorthand property) allow you to specify that a particular scrollbar in a particular named container can be used as the source for a scroll-driven animation. The scroll timeline can then be associated with an animation by setting the animation-timeline property to the name value defined using scroll-timeline-name.

When using the scroll-timeline shorthand property, the order of the property values must be scroll-timeline-name followed by scroll-timeline-axis. The longhand and shorthand properties are both available behind the preference.

You can alternatively use the scroll() functional notation with animation-timeline to indicate that a scrollbar axis in an ancestor element will be used for the timeline.

For more information, see Firefox bug 1807685, Firefox bug 1804573, Firefox bug 1809005, Firefox bug 1676791, Firefox bug 1754897, and Firefox bug 1737918.

Release channel Version added Enabled by default?
Nightly 110 No
Developer Edition 110 No
Beta 110 No
Release 110 No
Preference name layout.css.scroll-driven-animations.enabled

@font-face src feature checking

The @font-face src descriptor now supports the tech() function, allowing fallback of whether a font resource is downloaded based on whether the user-agent supports a particular font feature or technology. See Firefox bug 1715546 for more details.

Release channel Version added Enabled by default?
Nightly 105 Yes
Developer Edition 105 No
Beta 105 No
Release 105 No
Preference name layout.css.font-tech.enabled

font-variant-emoji

The CSS font-variant-emoji property allows you to set a default presentation style for displaying emojis. See (Firefox bug 1461589) for more details.

Release channel Version added Enabled by default?
Nightly 108 Yes
Developer Edition 108 No
Beta 108 No
Release 108 No
Preference name layout.css.font-variant-emoji.enabled

page-orientation

The page-orientation CSS descriptor for the @page at-rule controls the rotation of a printed page. It handles the flow of content across pages when the orientation of a page is changed. This behavior differs from the size descriptor in that a user can define the direction in which to rotate the page. See (Firefox bug 1673987) for more details.

Release channel Version added Enabled by default?
Nightly 111 Yes
Developer Edition 111 No
Beta 111 No
Release 111 No
Preference name layout.css.page-orientation.enabled

prefers-reduced-transparency media feature

The CSS prefers-reduced-transparency media feature lets you detect if a user has enabled the setting to minimize the amount of transparent or translucent layer effects on their device. See (Firefox bug 1736914) for more details.

Release channel Version added Enabled by default?
Nightly 113 No
Developer Edition 113 No
Beta 113 No
Release 113 No
Preference name layout.css.prefers-reduced-transparency.enabled

inverted-colors media feature

The CSS inverted-colors media feature lets you detect if a user agent or the underlying operating system is inverting colors. See (Firefox bug 1794628) for more details.

Release channel Version added Enabled by default?
Nightly 114 No
Developer Edition 114 No
Beta 114 No
Release 114 No
Preference name layout.css.inverted-colors.enabled

Named view progress timelines property

The CSS view-timeline-name property lets you give a name to particular element, identifying that its ancestor scroller element is the source of a view progress timeline. The name can then be assigned to the animation-timeline, which then animates the associated element as it moves through the visible area of its ancestor scroller. See (Firefox bug 1737920) for more details.

Release channel Version added Enabled by default?
Nightly 114 No
Developer Edition 114 No
Beta 114 No
Release 114 No
Preference name layout.css.scroll-driven-animations.enabled

Anonymous view progress timelines function

The CSS view() function lets you specify that the animation-timeline for an element is a view progress timeline, which will animate the element as it moves through the visible area of its ancestor scroller. The function defines the axis of the parent element that supplies the timeline, along with the inset within the visible area at which the animation starts and begins. See (Firefox bug 1808410) for more details.

Release channel Version added Enabled by default?
Nightly 114 No
Developer Edition 114 No
Beta 114 No
Release 114 No
Preference name layout.css.scroll-driven-animations.enabled

zoom property

The non-standard CSS zoom property is enabled in the Nightly release and lets you magnify an element similar to the transform property, but it affects the layout size of the element. See (Firefox bug 1855763 and Firefox bug 390936) for more details.

Release channel Version added Enabled by default?
Nightly 120 Yes
Developer Edition 120 No
Beta 120 No
Release 120 No
Preference name layout.css.zoom.enabled

To ensure compatibility with these changes, the Vendor-prefixed transform properties and the Vendor-prefixed transition properties are disabled in the Nightly release. These changes are described in the following sections.

text-wrap: balance & stable values

The text-wrap CSS property values balance and stable allow the layout of short content to be wrapped in a balanced manner and for editable content to not reflow while the user is editing it, respectively. (See Firefox bug 1731541 for more details.)

Release channel Version added Enabled by default?
Nightly 120 Yes
Developer Edition 120 No
Beta 120 No
Release 120 No
Preference name layout.css.text-wrap-balance.enabled, layout.css.text-wrap-balance.limit, layout.css.text-wrap-balance-after-clamp.enabled

Vendor-prefixed transform properties

The -moz- prefixed CSS transform properties have been disabled in the Nightly release via the layout.css.prefixes.transforms preference being set to false (Firefox bug 1855763). Specifically, the disabled properties are:

  • -moz-backface-visibility
  • -moz-perspective
  • -moz-perspective-origin
  • -moz-transform
  • -moz-transform-origin
  • -moz-transform-style
Release channel Version added Enabled by default?
Nightly 120 No
Developer Edition 120 Yes
Beta 120 Yes
Release 120 Yes
Preference name layout.css.prefixes.transforms

Vendor-prefixed transition properties

The -moz- prefixed CSS transitions properties have been disabled in the Nightly release via the layout.css.prefixes.transitions preference being set to false (Firefox bug 1855763). Specifically, the disabled properties are:

  • -moz-transition
  • -moz-transition-delay
  • -moz-transition-duration
  • -moz-transition-property
  • -moz-transition-timing-function
Release channel Version added Enabled by default?
Nightly 120 No
Developer Edition 120 Yes
Beta 120 Yes
Release 120 Yes
Preference name layout.css.prefixes.transitions

SVG

SVGPathSeg APIs

The SVGPathSeg APIs are being unshipped, and have been placed behind a preference. This includes: SVGPathSegList, SVGPathElement.getPathSegAtLength(), SVGAnimatedPathData. (See Firefox bug 1388931 for more details.)

Release channel Version removed Enabled by default?
Nightly 97 No
Developer Edition 97 No
Beta 97 No
Release 97 No
Preference name dom.svg.pathSeg.enabled

JavaScript

Intl.Segmenter

The Intl.Segmenter is supported in nightly builds, allowing developers to perform locale-sensitive text segmentation. This enables splitting a string into meaningful items (graphemes, words or sentences) in different locales. (See Firefox bug 1423593 for more details.)

Release channel Version added Enabled by default?
Nightly 122 Yes
Developer Edition NA No
Beta NA No
Release NA No
Preference name None

SharedArrayBuffer is growable

The SharedArrayBuffer is now growable using the SharedArrayBuffer.prototype.grow() method. The maximum allowed size of the buffer is specified using the options.maxByteLength parameter to the SharedArrayBuffer() constructor. The SharedArrayBuffer.prototype.growable and SharedArrayBuffer.prototype.maxByteLength properties indicate whether the buffer can be grow, and its maximum allowed size, respectively. (Firefox bug 1842773).

Release channel Version added Enabled by default?
Nightly 124 No
Developer Edition 124 No
Beta 124 No
Release 124 No
Preference name javascript.options.experimental.sharedarraybuffer_growable

ArrayBuffer is resizable

The ArrayBuffer can now be resized using the ArrayBuffer.prototype.resize() method. The maximum allowed size of the buffer is specified using the options.maxByteLength parameter to the ArrayBuffer() constructor. The ArrayBuffer.prototype.resizable and ArrayBuffer.prototype.maxByteLength properties indicate whether the buffer can be resized, and its maximum allowed size, respectively. (Firefox bug 1842773.)

Release channel Version added Enabled by default?
Nightly 124 No
Developer Edition 124 No
Beta 124 No
Release 124 No
Preference name javascript.options.experimental.arraybuffer_resizable

APIs

Graphics: Canvas, WebGL, and WebGPU

Hit regions

Whether the mouse coordinates are within a particular area on the canvas is a common problem to solve. The hit region API allows you to define an area of your canvas and provides another possibility to expose interactive content on a canvas to accessibility tools.

Release channel Version added Enabled by default?
Nightly 30 No
Developer Edition 30 No
Beta 30 No
Release 30 No
Preference name canvas.hitregions.enabled

WebGL: Draft extensions

When this preference is enabled, any WebGL extensions currently in "draft" status which are being tested are enabled for use. Currently, there are no WebGL extensions being tested by Firefox.

WebGPU API

The WebGPU API provides low-level support for performing computation and graphics rendering using the Graphics Processing Unit (GPU) of the user's device or computer. See Firefox bug 1602129 for our progress on this API.

Release channel Version added Enabled by default?
Nightly 113 Yes
Developer Edition 73 No
Beta 73 No
Release 73 No
Preference name dom.webgpu.enabled

WebRTC and media

The following experimental features include those found in the WebRTC API, the Web Audio API, the Media Source Extensions API, the Encrypted Media Extensions API, and the Media Capture and Streams API.

Asynchronous SourceBuffer add and remove

This adds the promise-based methods appendBufferAsync() and removeAsync() for adding and removing media source buffers to the SourceBuffer interface. See Firefox bug 1280613 and Firefox bug 778617 for more information.

Release channel Version added Enabled by default?
Nightly 62 No
Developer Edition 62 No
Beta 62 No
Release 62 No
Preference name media.mediasource.experimental.enabled

AVIF compliance strictness

The image.avif.compliance_strictness preference can be used to control the strictness applied when processing AVIF images. This allows Firefox users to display images that render on some other browsers, even if they are not strictly compliant.

Permitted values are:

  • 0: Accept images with specification violations in both recommendations ("should" language) and requirements ("shall" language), provided they can be safely or unambiguously interpreted.
  • 1 (default): Reject violations of requirements, but allow violations of recommendations.
  • 2: Strict. Reject any violations in requirements or recommendations.
Release channel Version added Default value
Nightly 92 1
Developer Edition 92 1
Beta 92 1
Release 92 1
Preference name image.avif.compliance_strictness

JPEG XL support

Firefox supports JPEG XL images if this feature is enabled. See Firefox bug 1539075 for more details.

Note that, as shown below, the feature is only available on Nightly builds (irrespective of whether the preference is set).

Release channel Version added Enabled by default?
Nightly 90 No
Developer Edition
Beta
Release
Preference name image.jxl.enabled

OpenFont COLRv1 fonts

This feature provides support for the OpenFont COLRv1 font specification. This enables compression-friendly color vector fonts with gradients, compositing and blending to be loaded using the CSS @font-face rule, or the CSS Font Loading API. See Firefox bug 1740530 for more details.

Release channel Version added Enabled by default?
Nightly 105 No
Developer Edition 105 No
Beta 105 No
Release 105 No
Preference name gfx.font_rendering.colr_v1.enabled

CSS Properties and Values API

The CSS Properties and Values API allows developers to register custom CSS properties through JavaScript via registerProperty() or in CSS using the @property at-rule. Registering properties using these two methods allows for type checking, default values, and properties that do or do not inherit values from their parent elements. See Firefox bug 1840480 for more details.

Release channel Version added Enabled by default?
Nightly 116 Yes
Developer Edition 116 No
Beta 116 No
Release 116 No
Preference name layout.css.property-and-value-api.enabled

CSS Custom Highlight API

The CSS Custom Highlight API provides a mechanism for styling arbitrary text ranges in a document (generalizing the behavior of other highlight pseudo-elements such as ::selection, ::spelling-error, ::grammar-error, and ::target-text). The ranges are defined in JavaScript using Range instances grouped in a Highlight, and then registered with a name using HighlightRegistry. The CSS ::highlight pseudo-element is used to apply styles to a registered highlight. See Firefox bug 1703961 for more details.

Release channel Version added Enabled by default?
Nightly 117 Yes
Developer Edition 117 No
Beta 117 No
Release 117 No
Preference name dom.customHighlightAPI.enabled

Service Workers

Preloading of service worker resources on navigation

The NavigationPreloadManager interface can be used to enable preloading of resources when navigating to a page. Preloading occurs in parallel with worker bootup, reducing the total time from start of navigation until resources are fetched.

Release channel Version added Enabled by default?
Nightly 99 yes
Developer Edition 97 No
Beta 97 No
Release 97 No
Preference name dom.serviceWorkers.navigationPreload.enabled

WebVR API

WebVR API (Disabled)

The deprecated WebVR API is on the path for removal. It is disabled by default on all builds Firefox bug 1750902.

Release channel Version removed Enabled by default?
Nightly 98 No
Developer Edition 98 No
Beta 98 No
Release 98 No
Preference name dom.vr.enabled

HTML DOM API

Shadow DOM

Firefox now supports the clonable option and property for shadow DOM.

  • The Element.attachShadow() method's clonable boolean option specifies whether the created shadow root is clonable: the default value is false but when set to true, the shadow host cloned with Node.cloneNode() or Document.importNode() will include shadow root in the copy.
  • The ShadowRoot interface's clonable read-only property returns true if the shadow root is clonable, and false otherwise.

When shadow root is created via declarative shadow DOM, the clonable option is set to true by default, and the clonable property returns true. (Firefox bug 1868428)

Release channel Version added Enabled by default?
Nightly 122 Yes
Developer Edition NA No
Beta NA No
Release NA No

Popover API

Firefox now supports the Popover API.

The following Web APIs are now implemented:

CSS updates include:

The following HTML global attributes are supported:

See Firefox bug 1823757 for more details.

Release channel Version added Enabled by default?
Nightly 122 Yes
Developer Edition 114 No
Beta 114 No
Release 114 No
Preference name dom.element.popover.enabled

HTMLMediaElement method: setSinkId()

HTMLMediaElement.setSinkId() allows you to set the sink ID of an audio output device on an HTMLMediaElement, thereby changing where the audio is being output. See Firefox bug 934425 for more details.

Release channel Version added Enabled by default?
Nightly 64 No
Developer Edition 64 No
Beta 64 No
Release 64 No
Preference name media.setsinkid.enabled

HTMLMediaElement properties: audioTracks and videoTracks

Enabling this feature adds the HTMLMediaElement.audioTracks and HTMLMediaElement.videoTracks properties to all HTML media elements. However, because Firefox doesn't currently support multiple audio and video tracks, the most common use cases for these properties don't work, so they're both disabled by default. See Firefox bug 1057233 for more details.

Release channel Version added Enabled by default?
Nightly 33 No
Developer Edition 33 No
Beta 33 No
Release 33 No
Preference name media.track.enabled

ClipboardItem

The ClipboardItem interface of the Clipboard API is now supported. It is available in nightly or early beta builds. (See Firefox bug 1809106 for more details.)

Release channel Version added Enabled by default?
Nightly 122 Yes
Developer Edition 87 No
Beta 122 Yes
Release 87 No
Preference name dom.events.asyncClipboard.clipboardItem

Clipboard read and write

The Clipboard.read(), Clipboard.readText(), and Clipboard.write() methods of the Clipboard interface are now available in nightly and early beta builds (See Firefox bug 1809106 for more details.)

Release channel Version added Enabled by default?
Nightly 122 Yes
Developer Edition 90 No
Beta 122 Yes
Release 90 No
Preference name dom.events.asyncClipboard.readText and dom.events.asyncClipboard.clipboardItem

HTML Sanitizer API

The HTML Sanitizer API allow developers to take untrusted strings of HTML and sanitize them for safe insertion into a document's DOM. Default elements within each configuration property (those to be sanitized) are still under consideration. Due to this the config parameter has not been implemented (see the constructor for more information). See Firefox bug 1673309 for more details.

Release channel Version added Enabled by default?
Nightly 84 No
Developer Edition 84 No
Beta 84 No
Release 84 No
Preference name dom.security.sanitizer.enabled

GeometryUtils methods: convertPointFromNode(), convertRectFromNode(), and convertQuadFromNode()

The GeometryUtils methods convertPointFromNode(), convertRectFromNode(), and convertQuadFromNode() map the given point, rectangle, or quadruple from the Node on which they're called to another node. (See Firefox bug 918189 for more details.)

Release channel Version added Enabled by default?
Nightly 31 Yes
Developer Edition 31 No
Beta 31 No
Release 31 No
Preference name layout.css.convertFromNode.enable

GeometryUtils method: getBoxQuads()

The GeometryUtils method getBoxQuads() returns the CSS boxes for a Node relative to any other node or viewport. (See Firefox bug 917755 for more details.)

Release channel Version added Enabled by default?
Nightly 31 Yes
Developer Edition 31 No
Beta 31 No
Release 31 No
Preference name layout.css.getBoxQuads.enabled

CustomStateSet and the :state() pseudo-class: States for custom elements

You can now define custom states for custom elements and match them using CSS. Custom states are represented as custom identifiers that can be added to, or removed from, the element's ElementInternals.states property (a CustomStateSet). The CSS :state() pseudo-class takes a custom identifier as an argument and matches the custom elements if the identifier is present in their set of states. (See Firefox bug 1861466 and Firefox bug 1866351 for more details.)

Release channel Version added Enabled by default?
Nightly 121 No
Developer Edition 121 No
Beta 121 No
Release 121 No
Preference name dom.element.customstateset.enabled

Payment Request API

Primary payment handling

The Payment Request API provides support for handling web-based payments within web content or apps. Due to a bug that came up during testing of the user interface, we have decided to postpone shipping this API while discussions over potential changes to the API are held. Work is ongoing. (See Firefox bug 1318984 for more details.)

Release channel Version added Enabled by default?
Nightly 55 No
Developer Edition 55 No
Beta 55 No
Release 55 No
Preference name dom.payments.request.enabled and
dom.payments.request.supportedRegions

WebShare API

The Web Share API allows sharing of files, URLs and other data from a site. This feature is enabled on Android in all builds, but behind a preference on Desktop (unless specified below).

Release channel Version changed Enabled by default?
Nightly 71 No (default). Yes (Windows from version 92)
Developer Edition 71 No
Beta 71 No
Release 71 No (Desktop). Yes (Android).
Preference name dom.webshare.enabled

Screen Orientation API

ScreenOrientation.lock()

The ScreenOrientation.lock() method allows a device to be locked to a particular orientation, if supported by the device and allowed by browser pre-lock requirements. Typically locking the orientation is only allowed on mobile devices when the document is being displayed full screen. See Firefox bug 1697647 for more details.

Release channel Version changed Enabled by default?
Nightly 111 Yes
Developer Edition 97 No
Beta 97 No
Release 97 No
Preference name dom.screenorientation.allow-lock

Screen Wake Lock API

The Screen Wake Lock API allows a web application to request that the screen not be dimmed or locked while it is active. This is useful for navigation and reading applications, and any application where the screen doesn't get regular tactile input while the application is in use (the default way to keep a screen awake). The API is accessed through Navigator.wakeLock in secure contexts, which returns a WakeLock. This can be used to request a WakeLockSentinel that can be used to monitor the status of the wake lock, and release it manually. See Firefox bug 1589554 for more details.

Release channel Version changed Enabled by default?
Nightly 122 Yes
Developer Edition 122 No
Beta 122 No
Release 122 No
Preference name dom.screenwakelock.enabled

Prioritized Task Scheduling API

The Prioritized Task Scheduling API provides a standardized way to prioritize all tasks belonging to an application, whether they defined in a website developer's code, or in third party libraries and frameworks.

This is enabled on Firefox Nightly (only) from Firefox 101. No preference is provided to allow it to be enabled in other releases.

Notifications API

Notifications have the requireInteraction property set to true by default on Windows systems and in the Nightly release (Firefox bug 1794475).

Release channel Version changed Enabled by default?
Nightly 117 Yes
Developer Edition 117 No
Beta 117 No
Release 117 Windows only
Preference name dom.webnotifications.requireinteraction.enabled

Web Codecs API

The Web Codecs API gives web developers low-level access to the individual frames of a video stream and chunks of audio. The following interfaces are supported (on Linux desktop only): VideoEncoder, VideoDecoder, EncodedVideoChunk, VideoFrame, VideoColorSpace. (Firefox bug 1874445).

Release channel Version changed Enabled by default?
Nightly 123 Yes. Linux desktop only.
Developer Edition 123 No
Beta 123 No
Release 123 No
Preference name dom.media.webcodecs.enabled

Security and privacy

Block plain text requests from Flash on encrypted pages

In order to help mitigate man-in-the-middle (MitM) attacks caused by Flash content on encrypted pages, a preference has been added to treat OBJECT_SUBREQUESTs as active content. See Firefox bug 1190623 for more details.

Release channel Version added Enabled by default?
Nightly 59 No
Developer Edition 59 No
Beta 59 No
Release 59 No
Preference name security.mixed_content.block_object_subrequest

Insecure page labeling

These two preferences add a "Not secure" text label in the address bar next to the traditional lock icon when a page is loaded insecurely (that is, using HTTP rather than HTTPS). See Firefox bug 1335970 for more details.

Release channel Version added Enabled by default?
Nightly 60 No
Developer Edition 60 No
Beta 60 No
Release 60 No
Preference name security.insecure_connection_text.enabled for normal browsing mode; security.insecure_connection_text.pbmode.enabled for private browsing mode

Upgrading mixed display content

When enabled, this preference causes Firefox to automatically upgrade requests for media content from HTTP to HTTPS on secure pages. The intent is to prevent mixed-content conditions in which some content is loaded securely while other content is insecure. If the upgrade fails (because the media's host doesn't support HTTPS), the media is not loaded. (See Firefox bug 1435733 for more details.)

This also changes the console warning; if the upgrade succeeds, the message indicates that the request was upgraded, instead of showing a warning.

Release channel Version added Enabled by default?
Nightly 84 Yes
Developer Edition 60 No
Beta 60 No
Release 60 No
Preference name security.mixed_content.upgrade_display_content

Permissions Policy / Feature policy

Permissions Policy allows web developers to selectively enable, disable, and modify the behavior of certain features and APIs in the browser. It is similar to CSP but controls features instead of security behavior. This is implemented in Firefox as Feature Policy, the name used in an earlier version of the specification.

Note that supported policies can be set through the allow attribute on <iframe> elements even if the user preference is not set.

Release channel Version added Enabled by default?
Nightly 65 No
Developer Edition 65 No
Beta 65 No
Release 65 No
Preference name dom.security.featurePolicy.header.enabled

Clear-Site-Data "cache" directive

The Clear-Site-Data HTTP response header cache directive clears the browser cache for the requesting website.

Note: This was originally enabled by default, but put behind a preference in version 94 (Firefox bug 1729291).

Release channel Version added Enabled by default?
Nightly 63 No
Developer Edition 63 No
Beta 63 No
Release 63 No
Preference name privacy.clearsitedata.cache.enabled

HTTP

SameSite=Lax by default

SameSite cookies have a default value of Lax. With this setting, cookies are only sent when a user is navigating to the origin site, not for cross-site subrequests to load images or frames into a third party site and so on. For more details see Firefox bug 1617609.

Release channel Version added Enabled by default?
Nightly 69 No
Developer Edition 69 No
Beta 69 No
Release 69 No
Preference name network.cookie.sameSite.laxByDefault

Access-Control-Allow-Headers wildcard does not cover Authorization

The Access-Control-Allow-Headers is a response header to a CORS preflight request, that indicates which request headers may be included in the final request. The response directive can contain a wildcard (*), which indicates that the final request may include all headers except the Authorization header.

By default, Firefox includes the Authorization header in the final request after receiving a response with Access-Control-Allow-Headers: *. Set the preference to false to ensure Firefox does not include the Authorization header. For more details see Firefox bug 1687364.

Release channel Version added Enabled by default?
Nightly 115 Yes
Developer Edition 115 Yes
Beta 115 Yes
Release 115 Yes
Preference name network.cors_preflight.authorization_covered_by_wildcard

Developer tools

Mozilla's developer tools are constantly evolving. We experiment with new ideas, add new features, and test them on the Nightly and Developer Edition channels before letting them go through to beta and release. The features below are the current crop of experimental developer tool features.

Execution context selector

This feature displays a button on the console's command line that lets you change the context in which the expression you enter will be executed. (See Firefox bug 1605154 and Firefox bug 1605153 for more details.)

Release channel Version added Enabled by default?
Nightly 75 No
Developer Edition 75 No
Beta 75 No
Release 75 No
Preference name devtools.webconsole.input.context

Mobile gesture support in Responsive Design Mode

Mouse gestures are used to simulate mobile gestures like swiping/scrolling, double-tap and pinch-zooming and long-press to select/open the context menu. (See Firefox bug 1621781, Firefox bug 1245183, and Firefox bug 1401304 for more details.)

Release channel Version added Enabled by default?
Nightly 76[1] Yes
Developer Edition 76[1] Yes
Beta 76[1] Yes
Release 76[1] No
Preference name n/a

[1] Support for zooming using the double-tap gesture was added in Firefox 76. The other gestures were added for Firefox 79.

Server-sent events in Network Monitor

The Network Monitor displays information for server-sent events. (See Firefox bug 1405706 for more details.)

Release channel Version added Enabled by default?
Nightly 80 Yes
Developer Edition 80 Yes
Beta 80 No
Release 80 No
Preference name devtools.netmonitor.features.serverSentEvents

CSS browser compatibility tooltips

The CSS Rules View can display browser compatibility tooltips next to any CSS properties that have known issues. For more information see: Examine and edit HTML > Browser Compat Warnings.

Release channel Version added Enabled by default?
Nightly 81 No
Developer Edition 81 No
Beta 81 No
Release 81 No
Preference name devtools.inspector.ruleview.inline-compatibility-warning.enabled

UI

Desktop zooming

This feature lets you enable smooth pinch zooming on desktop computers without requiring layout reflows, just like mobile devices do. (See Firefox bug 1245183 and Firefox bug 1620055 for more details.)

Release channel Version added Enabled by default?
Nightly 42 Yes
Developer Edition 42 No
Beta 42 No
Release 42 No
Preference name apz.allow_zooming and (on Windows) apz.windows.use_direct_manipulation

See also