Revision 1077578 of Firefox 46 for developers

<p><a href="https://www.mozilla.org/firefox/developer/" style="float: right; margin-bottom: 20px; padding: 10px; text-align: center; border-radius: 4px; display: inline-block; background-color: #81BC2E; white-space: nowrap; color: white; text-shadow: 0px 1px 0px rgba(0, 0, 0, 0.25); box-shadow: 0px 1px 0px 0px rgba(0, 0, 0, 0.2), 0px -1px 0px 0px rgba(0, 0, 0, 0.3) inset;">To test the latest developer features of Firefox,<br />
 install Firefox Developer Edition</a>Firefox 46 was released on April 26, 2016. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.</p>

<h2 id="Changes_for_Web_developers">Changes for Web developers</h2>

<h3 id="Developer_Tools">Developer Tools</h3>

<p>{{page('/en-US/docs/Tools/Release_notes', 'Firefox_46')}}</p>

<h3 id="HTML">HTML</h3>

<ul>
 <li>When faced with an invalid <code>type</code> value, {{HTMLElement("ul")}} no longer&nbsp;maps&nbsp;to&nbsp;<code>decimal</code>, but&nbsp;now behaves as if no&nbsp;<code>type</code> value were specified&nbsp;({{bug(241719)}}).</li>
 <li>The attribute <code>pattern</code> on {{HTMLElement("input")}} is now treated as {{jsxref("RegExp", "a regular expression", "", 1)}} with <code>"u"</code> (unicode) flag ({{bug(1227906)}}).</li>
</ul>

<h3 id="CSS">CSS</h3>

<ul>
 <li>Our implementation of CSS Grids has been updated:
  <ul>
   <li>The keywords <code>auto-fill</code> and <code>auto-fit</code> are now allowed in the <code>repeat()</code> function ({{bug(1118820)}}).</li>
   <li>The <code>true</code> value has been renamed to <code>unsafe</code>; this affects the properties {{cssxref("justify-content")}}, {{cssxref("align-content")}}, {{cssxref("justify-self")}}, {{cssxref("align-self")}}, {{cssxref("justify-items")}} and {{cssxref("align-items")}} ({{bug(1230478)}}).</li>
  </ul>
 </li>
 <li>The properties {{cssxref("text-emphasis")}}, {{cssxref("text-emphasis-style")}}, {{cssxref("text-emphasis-color")}} and {{cssxref("text-emphasis-position")}} are now enabled by defaut ({{bug(1231485)}}).</li>
 <li>Gecko now accepts the <code>-webkit-</code> prefixed version of <a href="https://wiki.mozilla.org/Compatibility/Mobile/Non_Standard_Compatibility">some properties</a>; it requires to switch <code>layout.css.prefixes.webkit</code> to <code>true</code> ({{bug(1213126)}}).</li>
 <li>The experimental support of the&nbsp;{{cssxref("@font/font-display", "font-display")}} descriptor (of {{cssxref("@font")}}; it requires to switch <code>layout.css.font-display.enabled</code> to <code>true</code> ({{bug(1157064)}}).</li>
 <li>Added support for <a href="/en-US/docs/Web/CSS/@media/-webkit-transform-3d"><code>@media (-webkit-transform-3d)</code></a> as a media query for 3D transform support, if about:config pref <code>layout.css.prefixes.webkit</code> is set to <code>true</code> ({{bug(1239799)}}).</li>
 <li>{{cssxref("linear-gradient()")}}&nbsp;support for the omission of <code>0deg</code> units ({{bug(1239153)}}).</li>
 <li>&nbsp;[css-align] "unsafe start" (formerly "true start") should serialize to "start" etc&nbsp;({{bug(1230398)}}).</li>
</ul>

<h3 id="JavaScript">JavaScript</h3>

<ul>
 <li>The&nbsp;ES2015 (ES6) {{jsxref("RegExp.prototype.unicode", "RegExp unicode (u) flag", "", 1)}} has been implemented ({{bug(1135377)}}).</li>
 <li>The ES2015 (ES6) block-level functions have been implemented ({{bug(1071646)}}).</li>
 <li>The ES2015 (ES6) {{jsxref("TypedArray.prototype.sort()")}} method has been implemented ({{bug(1121937)}}).</li>
 <li>The ES2015 (ES6) {{jsxref("Functions/arguments/@@iterator", "arguments[@@iterator]")}} has been implemented ({{bug(1067049)}}).</li>
 <li>The experimental <a href="https://tc39.github.io/ecmascript_sharedmem/shmem.html">EcmaScript Shared Memory API</a> has been implemented. See the {{jsxref("SharedArrayBuffer")}} and {{jsxref("Atomics")}} objects. To use this experimental API set <code>javascript.options.shared_memory</code> to <code>true</code> in about:config.</li>
 <li>Redeclaration of <code><a href="/en-US/docs/Web/JavaScript/Reference/Statements/let">let</a></code> and <code><a href="/en-US/docs/Web/JavaScript/Reference/Statements/const">const</a></code> variables now throws a {{jsxref("SyntaxError")}} instead of a {{jsxref("TypeError")}} as per the ECMAScript specification ({{bug(1198833)}}).</li>
 <li>In <a href="/en-US/docs/Web/JavaScript/Reference/Strict_mode">Strict mode</a>, setting properties on {{Glossary("primitive")}} values will now throw a {{jsxref("TypeError")}} ({{bug(603201)}}).</li>
 <li>The non-standard {{jsxref("WeakMap.prototype.clear()")}} and {{jsxref("WeakSet.prototype.clear()")}} methods have been removed ({{bug(1101817)}}).</li>
 <li>The non-standard, static <code>RegExp.multiline</code> property is now deprecated ({{bug(1220457)}}).</li>
 <li>Built-in accessor function names now have a "get" or "set" prefix ({{bug(1180290)}}, {{bug(1235656)}}).</li>
 <li>{{jsxref("Operators/Array_comprehensions", "JS1.7/JS1.8 (legacy) array comprehensions", "#Differences_to_the_older_JS1.7JS1.8_comprehensions", 1)}} and {{jsxref("Operators/Generator_comprehensions", "JS1.7/JS1.8 (legacy) generator comprehensions", "#Differences_to_the_older_JS1.7JS1.8_comprehensions", 1)}} have been removed ({{bug(1220564)}}).</li>
</ul>

<h3 id="InterfacesAPIsDOM">Interfaces/APIs/DOM</h3>

<h4 id="DOM_HTML_DOM">DOM &amp; HTML DOM</h4>

<ul>
 <li>The deprecated {{domxref("Window.showModalDialog()")}} method is no more available when Firefox runs in multi-process mode (e10s) ({{bug(1234700)}}).</li>
 <li>Added support for {{domxref("Document.elementsFromPoint")}} ({{bug(1164427)}}).</li>
 <li>When a non-existent option of a {{HTMLElement("select")}} element is programmatically selected, instead of being incorrectly left unchanged, the {{htmlattrxref("selectedIndex", "select")}} value is now set to <code>-1</code>, the {{htmlattrxref("selectedOptions", "select")}} to an empty {{domxref("HTMLCollection")}}, and {{htmlattrxref("value", "select")}} to an empty string ({{bug(1203668)}}).</li>
</ul>

<h4 id="Canvas">Canvas</h4>

<ul>
 <li>The remaining parts of the experimental {{domxref("OffscreenCanvas")}} API has been implemented; new features: {{domxref("OffscreenCanvas.OffscreenCanvas", "OffscreenCanvas()")}} constructor,&nbsp; {{domxref("OffscreenCanvas.toBlob()")}}, and {{domxref("OffscreenCanvas.transferToImageBitmap()")}}. To use this experimental API set <code>gfx.offscreencanvas.enabled</code> to <code>true</code> in about:config ({{bug(1172796)}}).</li>
 <li>The {{domxref("ImageBitmap.close()")}} method is now supported ({{bug(1172796)}}).</li>
 <li>A new {{domxref("ImageBitmapRenderingContext")}} rendering context is now implemented. Use <code>"bitmaprenderer"</code> with {{domxref("OffscreenCanvas.getContext()")}} or {{domxref("HTMLCanvasElement.getContext()")}} to obtain this context. ({{bug(1172796)}}).</li>
</ul>

<h4 id="WebGL">WebGL</h4>

<ul>
 <li>The {{domxref("WEBGL_compressed_texture_es3")}} extension has been implemented, allowing the use of <a href="https://en.wikipedia.org/wiki/Ericsson_Texture_Compression">ETC2 compressed texture formats </a>({{bug(917505)}}). To use this extension, set the preference <code>webgl.enable-draft-extensions</code> to <code>true</code> in about:config.</li>
</ul>

<h4 id="IndexedDB">IndexedDB</h4>

<p><em>No change.</em></p>

<h4 id="Service_Workers">Service Workers</h4>

<ul>
 <li>{{domxref("FetchEvent.request")}} is now non-nullable (see {{bug("1238213")}}.)</li>
 <li>{{domxref("Navigator.serviceWorker")}} has now been marked as SameObject (see {{bug("1238205")}}.)</li>
 <li>{{domxref("ExtendableMessageEvent.ports")}} has now been marked as SameObject (see {{bug("1238225")}}.)</li>
</ul>

<h4 id="Fetch">Fetch</h4>

<ul>
 <li>{{domxref("Request.mode")}} now has a new value available, <code>navigate</code>, for supporting requests generated while navigating between documents (see {{bug("1209081")}}.)</li>
</ul>

<h4 id="WebRTC">WebRTC</h4>

<p><em>No change.</em></p>

<h4 id="New_APIs">New APIs</h4>

<ul>
 <li>In SVG, the {{domxref("SVGStyleElement")}} interface now implements the {{domxref("LinkStyle")}} mixin ){{bug(1239128)}}.</li>
</ul>

<h4 id="Miscellaneous">Miscellaneous</h4>

<ul>
 <li>The asynchronous {{domxref("FileReader")}} is now available in Web workers ({{bug(901097)}}).</li>
 <li>Our experimental implementation of <a href="/en-US/docs/Web/API/Web_Animations_API">Web Animations API</a> has been updated:
  <ul>
   <li>{{domxref("AnimationEffectTimingReadOnly")}} and {{domxref("AnimationEffectReadOnly.timing")}} have been implemented ({{bug(1214536)}}).</li>
  </ul>
 </li>
 <li>The <a href="/en-US/docs/Web/API/Permissions_API">Permissions API</a> has now been enabled by default, for all release versions, not just Nightly as it previously was ({{bug(1221106)}}.)</li>
 <li>Sanitization of WOFF fonts has been loosened a bit ({{bug (1244693)}}).</li>
</ul>

<h3 id="MathML">MathML</h3>

<p><em>No change.</em></p>

<h3 id="SVG">SVG</h3>

<p><em>No change.</em></p>

<h3 id="AudioVideo">Audio/Video</h3>

<p><em>No change.</em></p>

<h2 id="HTTP">HTTP</h2>

<p><em>No change.</em></p>

<h2 id="Networking">Networking</h2>

<ul>
 <li>Support of {{rfc(7686)}} has been added: by default there is no attempt to resolve domain with the TLD <code>.onion</code>. This is controlled by the preference <code>network.dns.blockDotOnion</code>. Add-ons supporting Tor can swap this pref. ({{bug(1228457)}})</li>
</ul>

<h2 id="Security">Security</h2>

<p><em>No change.</em></p>

<h2 id="Changes_for_add-on_and_Mozilla_developers">Changes for add-on and Mozilla developers</h2>

<h3 id="Interfaces">Interfaces</h3>

<p><em>No change.</em></p>

<h3 id="XUL">XUL</h3>

<p><em>No change.</em></p>

<h3 id="JavaScript_code_modules">JavaScript code modules</h3>

<p><em>No change.</em></p>

<h3 id="XPCOM">XPCOM</h3>

<p><em>No change.</em></p>

<h3 id="Other">Other</h3>

<p><em>No change.</em></p>

<h2 id="See_also">See also</h2>

<ul>
 <li><a href="https://www.fxsitecompat.com/en-US/versions/46/">Site Compatibility for Firefox 46</a></li>
</ul>

<h2 id="Older_versions">Older versions</h2>

<p>{{Firefox_for_developers(45)}}</p>