In order to test new features, Mozilla publishes a test version of the Firefox browser, Firefox Nightly, every day. Experimental features, for example implementations of proposed Web platform standards, are available. This page lists features that are in Nightly versions of Firefox along with information on how to activate them, if necessary. You can test your Web sites and applications before these features get released and ensure everything will still work with the latest Web technology capabilities.

To test these experimental features, you need to download Firefox Nightly or Firefox Developer Edition.

HTML

Feature Firefox Nightly Firefox Developer Edition Firefox Beta Firefox Release Preference
Date and time inputs
The UI for the <input> date and time related input types.
Disabled
(available since 51)
Disabled
(available since 51)
Disabled
(available since 51)
--- dom.forms.datetime
<dialog>
Dialog element including some DOM API to interact with it.
Disabled
(available since 53)
Disabled
(available since 53)
--- --- dom.dialog_element.enabled

CSS

Feature Firefox Nightly Firefox Developer Edition Firefox Beta Firefox Release Preference
Subgrids Disabled Disabled Disabled Disabled layout.css.grid-template-subgrid-value.enabled
Logical values for clear and float CSS properties
The values clear: inline-start and clear: inline-end as well as float: inline-start and float: inline-end are making easier to create layouts that are agnostic to the text directionality.
45 45 Disabled Disabled layout.css.float-logical-values.enabled
Display stray control characters in CSS as hex boxes
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.
43 43 Disabled Disabled layout.css.control-characters.enabled
The transform-box property
Controls the box the relative values of transform-origin and transform relate too.
41 41 Disabled Disabled svg.transform-box.enabled
Basic shapes in clip-path
Adds the functions circle(), ellipse(), and polygon() to the set of possible values for clip-path. This is a part of CSS Masks Level 1.
53
(available disabled by default since 47)
53
(available disabled by default since 47)
Disabled
(available since 47, planned for 54)
Disabled
(available since 47, planned for 54)
layout.css.clip-path-shapes.enabled
Positioned CSS Masks
A subset of CSS Masks that includes longhand properties of CSS Masks, as well as a change in the shorthand property
51 51 53 Disabled
(planned for 53)
Controlled by a compile flag (MOZ_ENABLE_MASK_AS_SHORTHAND).
The font-display descriptor for @font-face
To improve Web fonts performance, @font-face has an experimental font-display descriptor.
Disabled
(available since 46)
Disabled
(available since 46)
Disabled
(available since 46)
Disabled
(available since 46)
layout.css.font-display.enabled

The font-variation-settings property
The font-variation-settings provides low-level control over OpenType or TrueType font typographic features, by specifying the four letter axis names of the features you want to vary, along with their variation values.

Disabled
(available since 53)
Disabled
(available since 53)
Disabled
(available since 53)
Disabled
(available since 53)

layout.css.font-variations.enabled
Functions only in Mac OS Sierra (and later).

For the downloadable fonts on axis-praxis, you also need gfx.downloadable_fonts.keep_variation_tables (in Firefox 54 and later)

The touch-action CSS property
The touch-action CSS property is part of the Pointer Events specification and allows to specify how and in what way the user is able to manipulate an object by touch.
50 layout.css.touch_action.enabled

The shape-outside CSS property
The shape-outside CSS property is part of the CSS Shapes Module Level 1 specification and allows to specify a float area causing inline contents to wrap around a shape.

Firefox currently implements the <shape-box> values (bug 1309467) as well as the circle() (bug 1311244) and ellipse() (bug 1326406) functions.

Disabled
(available since 53)
layout.css.shape-outside.enabled
The contain CSS property
The contain CSS property is part of the CSS Containment Module Level 1 specification and allows to indicate that an element and its contents are independent of the rest of the document tree, allowing user agents to optimize the rendering of a page.
Disabled
(available since 45)
Disabled
(available since 45)
Disabled
(available since 45)
Disabled
(available since 45)
layout.css.contain.enabled

JavaScript

See also ECMAScript Next support for implemented features of ECMAScript 2016 and later, that are not experimental and thus available without preferences in Firefox Release.

Feature Firefox Nightly Firefox Developer Edition Firefox Beta Firefox Release Preference
Additions to the ArrayBuffer object
Adds the ArrayBuffer.transfer() that returns a new ArrayBuffer whose contents have been taken from the oldBuffer's data (spec).
36 Disabled Disabled Disabled None
TypedObject objects (spec) Enabled Disabled Disabled Disabled None
SIMD (specification and polyfill) Enabled Disabled Disabled Disabled None
Shared Memory objects
SharedArrayBuffer
Atomics
46
 
51
(available behind the pref since 46)
Disabled
(available behind the pref since 46)
Disabled
(available behind the pref since 46)
javascript.options.shared_memory
for each...in removed from Gecko Disabled Enabled Enabled Enabled None

APIs

Canvas & WebGL

Feature Firefox Nightly Firefox Developer Edition Firefox Beta Firefox Release Preference
WEBGL_debug_renderer_info extension
The WEBGL_debug_renderer_info extension allows to transmit information useful to help debugging problems to the server.
42 42 Disabled Disabled webgl.enable-debug-renderer-info
OffscreenCanvas
The OffscreenCanvas interface provides a canvas that can be rendered off screen. It is available in both the window and worker contexts.
Disabled
(available since 44)
Disabled
(available since 44)
Disabled
(available since 44)
Disabled
(available since 44)
gfx.offscreencanvas.enabled
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 define an area of your canvas and provides another possibility to expose interactive content on a canvas to accessibility tools.
Disabled
(available since 30)
Disabled
(available since 30)
Disabled
(available since 30)
Disabled
(available since 30)
canvas.hitregions.enabled

 DOM

Feature Firefox Nightly Firefox Developer Edition Firefox Beta Firefox Release Preference
WebVR API
The WebVR API allows to control and use virtual reality devices.
46
A major update of the interface happened in version 51.
46
A major update of the interface happened in version 51.
Disabled Disabled dom.vr.enabled
FlyWeb
FlyWeb is a project at Mozilla focused on bringing a new set of APIs to the browser for advertising and discovering local-area web servers.
51 Disabled Disabled Disabled dom.flyweb.enabled
HTMLMediaElement.seekToNextFrame()
Part of an experimentation process around support non-real-time access to media for tasks including filtering, editing, and so forth, the HTMLMediaElement.seekToNextFrame() advances the the current play position to the next frame in the media.
49
(Fundamental update in version 50)
49
(Fundamental update in version 50)
Disabled Disabled media.seekToNextFrame.enabled
GeometryUtils.getBoxQuads() (bug 917755) 31 31 Disabled Disabled layout.css.getBoxQuads.enabled
GeometryUtils.convertPointFromNode(),
GeometryUtils.RectFromNode(), and
GeometryUtils.convertQuadFromNode()
(bug 918189)
31 31 Disabled Disabled layout.css.convertFromNode.enabled
Node.rootNode
The Node.rootNode property returns a Node object representing the topmost node in the tree, or the current node if it's the topmost node in the tree.
This feature is kept experimental as its naming poses Web compatibility problems. It will be renamed in the future.
48 48 Disabled Disabled dom.node.rootNode.enabled
Performance Observer API
The PerformanceObserver interface is used to observe performance measurement events and be notified of new performance entries as they are recorded in the browser's performance timeline.
49 Disabled Disabled Disabled dom.enable_performance_observer
WebVTT Regions API
WebVTT regions are parts of the video viewport that provide a rendering area for WebVTT cues. The VTTRegion is the interface exposing the WebVTT cues.
This interface is considered to be in flux and isn't therefore activated in any version by default.
Disabled
(Experimental implementation since version 30)
Disabled Disabled Disabled media.webvtt.regions.enabled
Support for audio and video tracks
Implements HTMLMediaElement.audioTracks and HTMLMediaElment.videoTracks.
Firefox doesn't support multiple audio or video tracks, preventing the most common use cases for these properties to work properly. That's why these properties are not activated by default in any version.
Disabled
(Experimental implementation since version 33)
Disabled Disabled Disabled media.track.enabled
Better value for Event.timestamp
The property Event.timestamp is returning a DOMHighResTimeStamp, but the value is not the time since but since the reboot. This change allow for returning a timestamp relative to the Unix epoch.
32 (Windows)
43 (Linux)
32 (Windows)
43 (Linux)
Disabled Disabled media.track.enabled
Pointer Events 50 Disabled Disabled Disabled dom.w3c_pointer_events.enabled
MediaDevices.ondevicechange and the devicechange event
The MediaDevices.ondevicechange event handler and corresponding devicechange event make it possible to detect and react when audio and video devices are attached to or removed from the computer.

Disabled
51 (Mac)

Enabled
52 (Mac)
52 (Windows)
52 (Linux)

Disabled
51 (Mac)

Enabled
52 (Mac)
52 (Windows)
52 (Linux)

Disabled
51 (Mac)

Enabled
52 (Mac)
52 (Windows)
52 (Linux)

Disabled
51 (Mac)

Enabled
52 (Mac)
52 (Windows)
52 (Linux)

media.ondevicechange.enabled
Intersection Observer API
The Intersection Observer API allows you to configure a callback that is called whenever one item, called a target, intersects either the device viewport or a specified element called.
Disabled
(available since 53)
dom.IntersectionObserver.enabled
Web Animations API: KeyframeEffect and KeyframeEffectReadOnly
The KeyframeEffectReadOnly.KeyframeEffectReadOnly() and KeyframeEffect.KeyframeEffect() constructors can be used to clone existing KeyframeEffectReadOnly object instances by being given the object to clone as their only parameter (see bug 1273784.)
52 52 Disabled Disabled None

Developer Tools

Feature Firefox Nightly Firefox Developer Edition Firefox Beta Firefox Release Preference
Debugger rewrite in HTML 52 52 Disabled Disabled devtools.debugger.new-debugger-frontend
Console rewrite in HTML 52 Disabled Disabled Disabled devtools.webconsole.new-frontend-enabled
Responsive Design Mode rewrite in HTML
A rewrite of Responsive Design Mode using HTML adds new features like a device selector (applies size, UA, dPR), UI redesign, and there's more still to come.
52 52 52 52 devtools.responsive.html.enabled
Experimental Performance tool options
Enables options in the UI for JIT optimizations, memory, etc.
41 Disabled Disabled Disabled devtools.performance.ui.experimental
Layout side panel
The Layout side panel allows to inspect and manage different CSS layout types like CSS Grid Layout.
Disabled
(available since 52)
Disabled
(available since 52)
Disabled
(available since 52)
Disabled
(available since 52)
devtools.layoutview.enabled

Other

Feature Firefox Nightly Firefox Developer Edition Firefox Beta Firefox Release Preference
TLS 1.3 Enabled Enabled Disabled Disabled security.tls.version.max to 4

See also

Document Tags and Contributors

 Last updated by: chrisdavidmills,