---
title: Firefoxにおける試験的機能
slug: Mozilla/Firefox/Experimental_features
translation_of: Mozilla/Firefox/Experimental_features
---
<p>{{FirefoxSidebar}}</p>

<p class="summary">新しい機能をテストするために、Mozilla は Firefox ブラウザのテスト版である <a href="https://nightly.mozilla.org/">Firefox Nightly</a> を毎日公開しています。提案されたWebプラットフォーム標準の実装など、実験的な機能が利用可能です。このページには、必要に応じて Nightly 版の Firefox の機能と、Firefox の起動方法に関する情報が掲載されています。これらの機能がリリースされる前に、Webサイトとアプリケーションをテストして、最新のWebテクノロジ機能ですべてが機能することを確認できます。</p>

<p>これらの試験的機能をテストするためには、 <a href="https://nightly.mozilla.org/">Firefox Nightly</a> または <a href="https://www.mozilla.org/en-US/firefox/developer/">Firefox Developer Edition</a>をダウンロードしインストールしておくことが必要です。</p>

<h2 id="HTML">HTML</h2>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Feature</th>
   <th scope="col">Firefox Nightly</th>
   <th scope="col">Firefox Developer Edition</th>
   <th scope="col">Firefox Beta</th>
   <th scope="col">Firefox Release</th>
   <th scope="col">Preference</th>
  </tr>
  <tr>
   <td><strong>{{HTMLElement("dialog")}}</strong><br>
    Dialog element including DOM APIs to interact with it. Implementation of modal dialogs and accessibility still missing.</td>
   <td>Disabled<br>
    <sub>(available since 53)</sub></td>
   <td>Disabled<br>
    <sub>(available since 53)</sub></td>
   <td>---</td>
   <td>---</td>
   <td><code>dom.dialog_element.enabled</code></td>
  </tr>
 </thead>
</table>

<h2 id="CSS">CSS</h2>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Feature</th>
   <th scope="col">Firefox Nightly</th>
   <th scope="col">Firefox Developer Edition</th>
   <th scope="col">Firefox Beta</th>
   <th scope="col">Firefox Release</th>
   <th scope="col">Preference</th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td><strong>Subgrids</strong></td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td><code>layout.css.grid-template-subgrid-value.enabled</code></td>
  </tr>
  <tr>
   <td><strong>Display stray control characters in CSS as hex boxes</strong><br>
    This feature renders control characters (Unicode category Cc) other than <em>tab</em> (<code>U+0009</code>), <em>line feed</em> (<code>U+000A</code>), <em>form feed</em> (<code>U+000C</code>), and <em>carriage return</em> (<code>U+000D</code>) as a hexbox when they are not expected.</td>
   <td>43</td>
   <td>43</td>
   <td><a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1329613">Disabled</a></td>
   <td><a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1329613">Disabled</a></td>
   <td><code>layout.css.control-characters.enabled</code> or <code>layout.css.control-characters.visible</code></td>
  </tr>
  <tr>
   <td><strong>Positioned CSS Masks</strong><br>
    A subset of CSS Masks that includes <a href="/en-US/docs/Web/CSS/CSS_Masks">longhand properties of CSS Masks</a>, as well as a change in the shorthand property</td>
   <td>51</td>
   <td>51</td>
   <td>53</td>
   <td><a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1251161">Disabled</a></td>
   <td>Controlled by a compile flag (MOZ_ENABLE_MASK_AS_SHORTHAND).</td>
  </tr>
  <tr>
   <td>
    <p><strong>The</strong> <strong><code>font-variation-settings</code> property</strong><br>
     The {{cssxref("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.</p>
   </td>
   <td>Disabled<br>
    <sub>(available since 53)</sub></td>
   <td>Disabled<br>
    <sub>(available since 53)</sub></td>
   <td>Disabled<br>
    <sub>(available since 53)</sub></td>
   <td>Disabled<br>
    <sub>(available since 53)</sub></td>
   <td>
    <p><code>layout.css.font-variations.enabled</code><br>
     Functions only in Mac OS Sierra (and later).<br>
     <br>
     For the downloadable fonts on axis-praxis, you also need <code>gfx.downloadable_fonts.keep_variation_tables</code> (in Firefox 54 and later)</p>
   </td>
  </tr>
  <tr>
   <td><strong>The <code>touch-action</code> CSS property</strong><br>
    The {{cssxref("touch-action")}} CSS property is part of the {{SpecName("Pointer Events")}} specification and allows you to specify how and in what way the user is able to manipulate an object by touch.</td>
   <td>50</td>
   <td>—</td>
   <td>—</td>
   <td>—</td>
   <td><code>layout.css.touch_action.enabled</code></td>
  </tr>
  <tr id="shape-outside">
   <td>
    <p><strong>The <code>shape-outside</code> CSS property</strong><br>
     The {{cssxref("shape-outside")}} CSS property is part of the {{SpecName("CSS Shapes")}} specification and allows you to specify a float area causing inline contents to wrap around a shape.</p>

    <p>Firefox currently implements the <code>&lt;shape-box&gt;</code> values ({{bug(1309467)}}) as well as the <code>circle()</code> ({{bug(1311244)}}), <code>ellipse()</code> ({{bug(1326406)}}), and <code>polygon()</code> ({{bug(1326409)}}) functions. {{cssxref("shape-outside")}} is animatable since Firefox 57 ({{bug(1289049)}}).</p>
   </td>
   <td>Disabled<br>
    <sub>(available since 53)</sub></td>
   <td>—</td>
   <td>—</td>
   <td>—</td>
   <td><code>layout.css.shape-outside.enabled</code></td>
  </tr>
  <tr>
   <td><strong>The <code>contain</code> CSS property</strong><br>
    The {{cssxref("contain")}} CSS property is part of the {{SpecName("CSS Containment")}} specification and allows you to indicate that an element and its contents are independent of the rest of the document tree, allowing {{Glossary("User agent", "user agents")}} to optimize the rendering of a page.</td>
   <td>Disabled<br>
    <sub>(available since 45)</sub></td>
   <td>Disabled<br>
    <sub>(available since 45)</sub></td>
   <td>Disabled<br>
    <sub>(available since 45)</sub></td>
   <td>Disabled<br>
    <sub>(available since 45)</sub></td>
   <td><code>layout.css.contain.enabled</code></td>
  </tr>
  <tr id="column-span">
   <td>
    <p><strong>The <code>column-span</code> CSS property</strong><br>
     The {{cssxref("column-span")}} CSS property is part of the {{SpecName("CSS3 Multicol")}} specification and allows you to specify how many columns an element spans across.</p>

    <p>Firefox currently only parses the property ({{bug(1339298)}}), it's not actually implemented yet ({{bug(616436)}}).</p>
   </td>
   <td>Disabled<br>
    <sub>(recognized since 55, but not implemented yet)</sub></td>
   <td>—</td>
   <td>—</td>
   <td>—</td>
   <td><code>layout.css.column-span.enabled</code></td>
  </tr>
  <tr>
   <td><strong>The <code>frames()</code> timing function</strong><br>
    See <a href="https://developer.mozilla.org/en-US/docs/Web/CSS/single-transition-timing-function#The_frames()_class_of_timing-functions">The frames() class of timing-functions</a> for more details.</td>
   <td>Enabled</td>
   <td><sub>N/A</sub></td>
   <td>Disabled<br>
    <sub>(available since 55)</sub></td>
   <td>Disabled<br>
    <sub>(available since 55)</sub></td>
   <td>None</td>
  </tr>
 </tbody>
</table>

<h2 id="JavaScript">JavaScript</h2>

<p id="ECMAScript_2016">See also <a href="/en-US/docs/Web/JavaScript/New_in_JavaScript/ECMAScript_Next_support_in_Mozilla">ECMAScript Next support</a> for implemented features of ECMAScript 2016 and later, that are not experimental and thus available without preferences in Firefox Release.</p>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Feature</th>
   <th scope="col">Firefox Nightly</th>
   <th scope="col">Firefox Developer Edition</th>
   <th scope="col">Firefox Beta</th>
   <th scope="col">Firefox Release</th>
   <th scope="col">Preference</th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td><strong>Additions to the <code>ArrayBuffer</code> object</strong><br>
    Adds the {{jsxref("ArrayBuffer.transfer()")}} that returns a new <code>ArrayBuffer</code> whose contents have been taken from the <code>oldBuffer</code>'s data (<a href="https://gist.github.com/lukewagner/2735af7eea411e18cf20">spec</a>).</td>
   <td>36</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td>None</td>
  </tr>
  <tr>
   <td><strong>TypedObject objects</strong> (<a href="https://github.com/dslomov-chromium/typed-objects-es7">spec</a>)</td>
   <td>Enabled</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td>None</td>
  </tr>
  <tr>
   <td><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/SIMD">SIMD</a> (<a href="https://github.com/johnmccutchan/ecmascript_simd">specification and polyfill</a>)</td>
   <td>Enabled</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td>None</td>
  </tr>
  <tr>
   <td><strong>ECMAScript modules</strong><br>
    Allows you to use native ECMAScript modules, for example defining modules with <code>&lt;script type="module"&gt;</code>, defining fallback scripts with <code>&lt;script nomodule&gt;</code>, and <a href="/en-US/docs/Web/JavaScript/Reference/Statements/import">importing</a> code features that have been <a href="/en-US/docs/Web/JavaScript/Reference/Statements/export">exported</a> from modules.</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td><code>dom.moduleScripts.enabled</code></td>
  </tr>
 </tbody>
</table>

<h2 id="APIs">APIs</h2>

<h3 id="Canvas_WebGL">Canvas &amp; WebGL</h3>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Feature</th>
   <th scope="col">Firefox Nightly</th>
   <th scope="col">Firefox Developer Edition</th>
   <th scope="col">Firefox Beta</th>
   <th scope="col">Firefox Release</th>
   <th scope="col">Preference</th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td><strong><code>WEBGL_debug_renderer_info</code> extension</strong><br>
    The {{domxref("WEBGL_debug_renderer_info")}} extension allows you to transmit information useful to help debugging problems to the server.</td>
   <td>42</td>
   <td>42</td>
   <td><a href="https://bugzilla.mozilla.org/show_bug.cgi?id=742798">Disabled</a></td>
   <td><a href="https://bugzilla.mozilla.org/show_bug.cgi?id=742798">Disabled</a></td>
   <td><code>webgl.enable-debug-renderer-info</code></td>
  </tr>
  <tr>
   <td><strong>OffscreenCanvas</strong><br>
    The {{domxref("OffscreenCanvas")}} interface provides a canvas that can be rendered off screen. It is available in both the window and <a href="/en-US/docs/Web/API/Web_Workers_API">worker</a> contexts.</td>
   <td>Disabled<br>
    <sub>(available since 44)</sub></td>
   <td>Disabled<br>
    <sub>(available since 44)</sub></td>
   <td>Disabled<br>
    <sub>(available since 44)</sub></td>
   <td>Disabled<br>
    <sub>(available since 44)</sub></td>
   <td><code>gfx.offscreencanvas.enabled</code></td>
  </tr>
  <tr>
   <td><strong><a href="/en-US/docs/Web/API/Canvas_API/Tutorial/Hit_regions_and_accessibility">Hit regions</a></strong><br>
    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.</td>
   <td>Disabled<br>
    <sub>(available since 30)</sub></td>
   <td>Disabled<br>
    <sub>(available since 30)</sub></td>
   <td>Disabled<br>
    <sub>(available since 30)</sub></td>
   <td>Disabled<br>
    <sub>(available since 30)</sub></td>
   <td><code>canvas.hitregions.enabled</code></td>
  </tr>
  <tr>
   <td><strong><a href="/en-US/docs/Web/API/Streams_API">Streams API</a></strong><br>
    Allows JavaScript to programmatically access streams of data received over the network and process them as desired by the developer.</td>
   <td>Disabled<br>
    <sub>(available since 57)</sub></td>
   <td>Disabled<br>
    <sub>(available since 57)</sub></td>
   <td>Disabled<br>
    <sub>(available since 57)</sub></td>
   <td>Disabled<br>
    <sub>(available since 57)</sub></td>
   <td><code>dom.streams.enabled</code> and <code>javascript.options.streams</code></td>
  </tr>
 </tbody>
</table>

<h3 id="DOM">DOM</h3>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Feature</th>
   <th scope="col">Firefox Nightly</th>
   <th scope="col">Firefox Developer Edition</th>
   <th scope="col">Firefox Beta</th>
   <th scope="col">Firefox Release</th>
   <th scope="col">Preference</th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td><strong>WebVR API 1.1 on Mac</strong><br>
    The <a href="/en-US/docs/Web/API/WebVR_API">WebVR API</a> allows you to control and use virtual reality devices.</td>
   <td>Enabled</td>
   <td>Enabled</td>
   <td>Enabled</td>
   <td>Disabled</td>
   <td><code>dom.vr.enabled</code></td>
  </tr>
  <tr>
   <td><strong>Gamepad extensions</strong><br>
    <a href="/en-US/docs/Web/API/Gamepad_API#Experimental_Gamepad_extensions">The Gamepad Extensions</a> provide access to additional functionality such as pose information in the case of WebVR controllers, and haptic actuator control (e.g. controller vibration hardware).</td>
   <td>Enabled</td>
   <td>Enabled</td>
   <td>Enabled</td>
   <td>Disabled</td>
   <td><code>dom.gamepad-extensions.enabled</code></td>
  </tr>
  <tr>
   <td><strong>FlyWeb</strong><br>
    <a href="https://flyweb.github.io/">FlyWeb</a> is a project at Mozilla focused on bringing a new set of APIs to the browser for advertising and discovering local-area web servers.</td>
   <td>51</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td><code>dom.flyweb.enabled</code></td>
  </tr>
  <tr>
   <td><code><strong>HTMLMediaElement.seekToNextFrame()</strong></code><br>
    Part of an experimentation process around support non-real-time access to media for tasks including filtering, editing, and so forth, the {{domxref("HTMLMediaElement.seekToNextFrame()")}} advances the the current play position to the next frame in the media.</td>
   <td>49<br>
    <sub>(Fundamental update in version 50)</sub></td>
   <td>49<br>
    <sub>(Fundamental update in version 50)</sub></td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td><code>media.seekToNextFrame.enabled</code></td>
  </tr>
  <tr>
   <td><strong><code>GeometryUtils.getBoxQuads()</code></strong> ({{bug(917755)}})</td>
   <td>31</td>
   <td>31</td>
   <td><a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1107559">Disabled</a></td>
   <td><a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1107559">Disabled</a></td>
   <td><code>layout.css.getBoxQuads.enabled</code></td>
  </tr>
  <tr>
   <td><strong><code>GeometryUtils.convertPointFromNode()</code></strong>,<br>
    <strong><code>GeometryUtils.RectFromNode()</code></strong>, and<br>
    <code><strong>GeometryUtils.convertQuadFromNode()</strong></code><br>
    ({{bug(918189)}})</td>
   <td>31</td>
   <td>31</td>
   <td><a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1107559">Disabled</a></td>
   <td><a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1107559">Disabled</a></td>
   <td><code>layout.css.convertFromNode.enabled</code></td>
  </tr>
  <tr>
   <td><strong><code>Node.rootNode</code></strong><br>
    The {{domxref("Node.rootNode")}} property returns a {{domxref("Node")}} object representing the topmost node in the tree, or the current node if it's the topmost node in the tree.<br>
    <em>This feature is kept experimental as its naming poses Web compatibility problems. It will be renamed in the future.</em></td>
   <td>48</td>
   <td>48</td>
   <td><a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1269155">Disabled</a></td>
   <td><a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1269155">Disabled</a></td>
   <td><code>dom.node.rootNode.enabled</code></td>
  </tr>
  <tr>
   <td><strong>WebVTT Regions API</strong><br>
    <a href="/en-US/docs/Web/API/Web_Video_Text_Tracks_Format">WebVTT</a> regions are parts of the video viewport that provide a rendering area for WebVTT cues. The {{domxref("VTTRegion")}} is the interface exposing the WebVTT cues.<br>
    <em>This interface is considered to be in flux and isn't therefore activated in any version by default.</em></td>
   <td>Disabled<br>
    <sub>(Experimental implementation since version 30)</sub></td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td><code>media.webvtt.regions.enabled</code></td>
  </tr>
  <tr>
   <td><strong>Support for audio and video tracks</strong><br>
    Implements {{domxref("HTMLMediaElement.audioTracks")}} and {{domxref("HTMLMediaElement.videoTracks")}}.<br>
    <em>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.</em></td>
   <td>Disabled<br>
    <sub>(Experimental implementation since version 33)</sub></td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td><code>media.track.enabled</code></td>
  </tr>
  <tr>
   <td><strong>Better value for <code>Event.timestamp</code></strong><br>
    The property {{domxref("Event.timestamp")}} is returning a {{domxref("DOMHighResTimeStamp")}}, which is now relative to the Unix epoch.</td>
   <td>32 (Windows)<br>
    43 (Linux)</td>
   <td>32 (Windows)<br>
    43 (Linux)</td>
   <td><a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1026804">Disabled</a></td>
   <td><a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1026804">Disabled</a></td>
   <td><code>media.track.enabled</code></td>
  </tr>
  <tr id="pointer-events">
   <td><strong>Pointer Events</strong></td>
   <td>50</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td><code>dom.w3c_pointer_events.enabled</code></td>
  </tr>
  <tr>
   <td><strong>Pointer Events {{domxref("PointerEvent.tangentialPressure")}} and {{domxref("PointerEvent.twist")}}</strong></td>
   <td>54</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td><code>dom.w3c_pointer_events.enabled</code></td>
  </tr>
  <tr>
   <td><strong>Intersection Observer API</strong><br>
    The {{domxref("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.</td>
   <td>Disabled<br>
    <sub>(available since 53)</sub></td>
   <td>—</td>
   <td>—</td>
   <td>—</td>
   <td><code>dom.IntersectionObserver.enabled</code></td>
  </tr>
  <tr>
   <td><strong><a href="/en-US/docs/Web/API/Web_Animations_API">Web Animations API: KeyframeEffect and KeyframeEffectReadOnly</a></strong><br>
    The {{domxref("KeyframEffectReadOnly()", "KeyframeEffectReadOnly.KeyframeEffectReadOnly()")}} and {{domxref("KeyframeEffect()", "KeyframeEffect.KeyframeEffect()")}} constructors can be used to clone existing {{domxref("KeyframeEffectReadOnly")}} object instances by being given the object to clone as their only parameter (see {{bug(1273784)}}.)</td>
   <td>52</td>
   <td>52</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td>None</td>
  </tr>
  <tr>
   <td><strong>{{domxref("PromiseRejectionEvent")}} and related features</strong><br>
    Providing a way to monitor and more finely control the rejection of Promises.<br>
     </td>
   <td>Disabled<br>
    <sub>(available since 55)</sub></td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td><code>dom.promise_rejection_events.enabled</code></td>
  </tr>
  <tr>
   <td><strong><a href="/en-US/docs/Web/API/Payment_Request_API">Payment Request API</a></strong><br>
    Provides a web API for handling web-based payments.</td>
   <td>Disabled<br>
    <sub>(available since 55)</sub></td>
   <td>Disabled<br>
    <sub>(available since 55)</sub></td>
   <td>Disabled<br>
    <sub>(available since 55)</sub></td>
   <td>Disabled<br>
    <sub>(available since 55)</sub></td>
   <td><code>dom.payments.request.enabled</code></td>
  </tr>
  <tr>
   <td><strong>Basic Card Payment API</strong><br>
    Provides dictionaries that define data structures describing card payment types and payment responses for use in the Payment Request API. See {{domxref("BasicCardRequest")}} and {{domxref("BasicCardResponse")}}.</td>
   <td>Disabled<br>
    <sub>(available since 56)</sub></td>
   <td>Disabled<br>
    <sub>(available since 56)</sub></td>
   <td>Disabled<br>
    <sub>(available since 56)</sub></td>
   <td>Disabled<br>
    <sub>(available since 56)</sub></td>
   <td><code>dom.payments.request.enabled</code></td>
  </tr>
  <tr>
   <td>The proprietary {{domxref("Window.content")}} property is now only available to chrome (privileged) code, and not available to the web anymore ({{bug(864845)}}).</td>
   <td>Enabled<br>
    <sub>(since 57)</sub></td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td> </td>
  </tr>
 </tbody>
</table>

<h3 id="WebRTC">WebRTC</h3>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Feature</th>
   <th scope="col">Firefox Nightly</th>
   <th scope="col">Firefox Developer Edition</th>
   <th scope="col">Firefox Beta</th>
   <th scope="col">Firefox Release</th>
   <th scope="col">Preference</th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td><strong>TCP ICE candidates</strong><br>
    ICE candidates that use TCP rather than UDP are considered during ICE negotiation.</td>
   <td>
    <p>Disabled<br>
     41</p>

    <p>Enabled<br>
     54</p>
   </td>
   <td>Disabled<br>
    41</td>
   <td>Disabled<br>
    41</td>
   <td>Disabled<br>
    41</td>
   <td><code>media.peerconnection.ice.tcp</code></td>
  </tr>
 </tbody>
</table>

<h2 id="開発者用ツール">開発者用ツール</h2>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Feature</th>
   <th scope="col">Firefox Nightly</th>
   <th scope="col">Firefox Developer Edition</th>
   <th scope="col">Firefox Beta</th>
   <th scope="col">Firefox Release</th>
   <th scope="col">Preference</th>
  </tr>
 </thead>
 <tbody>
  <tr id="new-debugger-frontend">
   <td><strong>Debugger rewrite in HTML</strong></td>
   <td>52</td>
   <td>52</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td><code>devtools.debugger.new-debugger-frontend</code></td>
  </tr>
  <tr id="new-console-frontend">
   <td><strong>Console rewrite in HTML</strong></td>
   <td>52</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td><code>devtools.webconsole.new-frontend-enabled</code></td>
  </tr>
  <tr id="performance-tool-options">
   <td><strong>Experimental Performance tool options</strong><br>
    Enables options in the UI for JIT optimizations, memory, etc.</td>
   <td>41</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td><code>devtools.performance.ui.experimental</code></td>
  </tr>
  <tr id="layout-side-panel">
   <td><strong>Layout side panel</strong><br>
    The Layout side panel allows to inspect and manage different CSS layout types like <a href="/en-US/docs/Web/CSS/CSS_Grid_Layout">CSS Grid Layout</a>.</td>
   <td>Disabled<br>
    <sub>(available since 52)</sub></td>
   <td>Disabled<br>
    <sub>(available since 52)</sub></td>
   <td>Disabled<br>
    <sub>(available since 52)</sub></td>
   <td>Disabled<br>
    <sub>(available since 52)</sub></td>
   <td><code>devtools.layoutview.enabled</code></td>
  </tr>
 </tbody>
</table>

<h2 id="セキュリティ">セキュリティ</h2>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Feature</th>
   <th scope="col">Firefox Nightly</th>
   <th scope="col">Firefox Developer Edition</th>
   <th scope="col">Firefox Beta</th>
   <th scope="col">Firefox Release</th>
   <th scope="col">Preference</th>
  </tr>
  <tr>
   <td><strong>TLS 1.3</strong></td>
   <td>Enabled</td>
   <td>Enabled</td>
   <td>Disabled</td>
   <td>Disabled</td>
   <td><code>security.tls.version.max</code> to <code>4</code></td>
  </tr>
  <tr>
   <td><strong>Blocking data URL navigations on the top-level window</strong><br>
    We are experimenting with blocking <code>data:</code> URLs on the top-level window. See <a href="https://www.fxsitecompat.com/en-CA/docs/2017/data-url-navigations-on-top-level-window-will-be-blocked/">Data URL navigations on top level window will be blocked</a> for a detailed explanation.</td>
   <td>Enabled</td>
   <td>n/a</td>
   <td>Enabled</td>
   <td>Disabled</td>
   <td><code>security.data_uri.block_toplevel<br>
    _data_uri_navigations</code></td>
  </tr>
 </thead>
</table>

<h2 id="その他">その他</h2>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Feature</th>
   <th scope="col">Firefox Nightly</th>
   <th scope="col">Firefox Developer Edition</th>
   <th scope="col">Firefox Beta</th>
   <th scope="col">Firefox Release</th>
   <th scope="col">Preference</th>
  </tr>
  <tr>
   <td><a href="https://support.mozilla.org/t5/Other/How-to-add-a-shortcut-to-a-website-on-Android/ta-p/21992"><strong>Add to home screen</strong></a><br>
    The <code>icons</code>, <code>name</code>, <code>short_name</code>, and <code>theme_color</code> fields of the <a href="/en-US/docs/Web/Manifest">Web App Manifest</a> (if present) can now be as the source of the homescreen/apps window icons, apps window title, homescreen icon title, and apps window color (respectively) for "Add to home screen" (Firefox Mobile only).</td>
   <td>Disabled<br>
    <sub>(available since 53)</sub></td>
   <td>Disabled<br>
    <sub>(available since 53)</sub></td>
   <td>Disabled<br>
    <sub>(available since 53)</sub></td>
   <td>Disabled<br>
    <sub>(available since 52)</sub></td>
   <td><code>manifest.install.enabled</code></td>
  </tr>
 </thead>
</table>

<h2 id="次も参照してください">次も参照してください</h2>

<ul>
 <li><a href="/en-US/docs/Mozilla/Firefox/Releases">Firefox developer release notes</a></li>
 <li><a href="https://nightly.mozilla.org/">Firefox Nightly</a></li>
 <li><a href="https://www.mozilla.org/en-US/firefox/developer/">Firefox Developer Edition</a></li>
</ul>