---
title: Firefox 28 for developers
slug: Mozilla/Firefox/Releases/28
translation_of: Mozilla/Firefox/Releases/28
---
<div>{{FirefoxSidebar}}</div>

<p>Firefox 28 wurde am 18. März 2014 veröffentlicht. Dieser Artikel listet wichtige Änderungen, die sowohl für Webentwickler, als auch für Firefox-, Gecko- und AddOn-Entwickler nützlich sind.</p>

<h2 id="Änderungen_für_Web-Entwickler">Änderungen für Web-Entwickler</h2>

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

<ul>
 <li>Die {{domxref("console.exception")}} Eigenschaft wurde hinzugefügt ({{bug("922214")}}).</li>
 <li>Die {{domxref("console.assert")}} Eigenschaft wurde hinzugefügt ({{bug("760193")}}).</li>
 <li>App Manager: ein neuer Manifest-Texteditor wurde hinzugefügt.</li>
 <li>App-Manager: die Toolbox für die Fehlersuche von Apps ist jetzt in die Benutzeroberfläche des App Managers integriert.</li>
 <li>Web-Konsole: ein "split console"-Modus wurde hinzugefügt - drücken Sie die Abbruchtaste, um die Konsole in anderen Tools schnell zu öffnen.</li>
 <li>Web-Konsole: ein dunkles Theme wurde für den Output hinzugefügt.</li>
 <li>Fehlersuche: lesbares minifiziertes JavaScript.</li>
 <li>Fehlersuche: einfach den Mauszeiger über eine Variable bewegen oder diese anklicken, um ein Popup für den derzeitigen Wert anzuzeigen.</li>
 <li>Inspector: ein Farbwähler und diverse Tooltips wurden der Regel-Ansicht hinzugefügt.</li>
 <li>Browser Toolbox: erlaubt AddOn- und Platformentwicklern die Benutzung von fast allen Entwickler-Tools während der Erfassung des Browsers.</li>
</ul>

<p>Mehr Einzelheiten in <a href="https://hacks.mozilla.org/2013/12/split-console-pretty-print-minified-js-and-more-firefox-developer-tools-episode-28/" title="Split console, pretty-print minified JS and more – Firefox Developer Tools Episode 28">diesem Beitrag</a>.</p>

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

<ul>
 <li>Support for multi-line <a href="/en-US/docs/Web/Guide/CSS/Flexible_boxes">flexbox</a> has been added ({{bug("939901")}}).</li>
 <li><span id="summary_alias_container"><span id="short_desc_nonedit_display">Longhand East Asian <a href="/en-US/docs/Web/CSS/list-style-type">counter styles</a></span></span> have been implemented ({{bug("934072")}}).</li>
 <li><span id="summary_alias_container"><span id="short_desc_nonedit_display">Experimental support for the {{cssxref("background-blend-mode")}} property has been added, but is disabled by default</span></span> ({{bug("841601")}}).</li>
 <li>The <code>none</code> value has been added to {{cssxref("font-variant-ligatures")}} ({{bug("913264")}}).</li>
 <li>Support for the {{cssxref(":hover")}} user action pseudo-class on pseudo-elements has been implemented ({{bug("922669")}}).</li>
</ul>

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

<ul>
 <li><code>&lt;input type=color&gt;</code> and <code>&lt;input type=number&gt;</code> have been implemented, disabled by default.</li>
</ul>

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

<ul>
 <li><a href="/en-US/docs/Web/JavaScript/ECMAScript_6_support_in_Mozilla" title="/en-US/docs/Web/JavaScript/ECMAScript_6_support_in_Mozilla">ECMAScript 2015</a> implementation continues:

  <ul>
   <li>New <code>Array</code> methods have been implemented: {{jsxref("Array.prototype.entries()")}} and {{jsxref("Array.prototype.keys()")}} ({{bug("894658")}}).</li>
  </ul>
 </li>
 <li>A bug causing that {{jsxref("Object.getOwnPropertyNames()")}} did not see unresolved properties of {{jsxref("Error")}} objects has been fixed ({{bug("724768")}}).</li>
</ul>

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

<ul>
 <li><span id="summary_alias_container"><span id="short_desc_nonedit_display"><code>HTMLVideoElement.canPlayType('video/webm')</code> now reports <code>maybe</code>.</span></span> ({{bug("884275")}}).</li>
 <li>The {{domxref("DocumentFragment.getElementById()")}} method has been implemented. E.g. <code>document.createDocumentFragment().getElementById()</code> ({{bug("933193")}}).</li>
 <li>The {{domxref("KeyboardEvent.repeat")}} attribute has been implemented ({{bug("600117")}}).</li>
 <li>The {{domxref("File")}} constructor, e.g. <code>new File(["foo"], "foo.txt")</code> has been implemented. ({{bug("819900")}}).</li>
 <li>The {{domxref("NavigatorPlugins.plugins", "navigator.plugins")}} is no more enumerable, for privacy reasons ({{bug(757726)}}).</li>
 <li>The two attributes {{domxref("Window.screenX")}} and {{domxref("Window.screenY")}} now return CSS pixels (and no more device pixels) ({{bug(943668)}}).</li>
 <li>The two methods {{domxref("CanvasRenderingContext2D.drawSystemFocusRing()")}} and {{domxref("CanvasRenderingContext2D.drawCustomFocusRing()")}} have been implemented. The preference <code>canvas.focusring.enabled</code> must be set to <code>true</code> to activate both ({{bug(540456)}}).</li>
 <li>The <code>willReadFrequently</code> context attribute for "<code>2d</code>" canvas contexts has been implemented (see {{domxref("HTMLCanvasElement.getContext()")}}) ({{bug(884226)}}).</li>
 <li>The following attributes and methods of {{domxref("NavigatorID")}} have been implemented on {{domxref("WorkerNavigator")}} to allow their use in workers: {{domxref("NavigatorID.appCodeName", "appCodeName")}}, {{domxref("NavigatorID.product", "product")}}, and {{domxref("NavigatorID.taintEnabled", "taintEnabled()")}} ({{bug(925847)}}).</li>
 <li>The {{domxref("NonDocumentTypeChildNode.previousElementSibling" , "previousElementSibling")}} and {domxref("NonDocumentTypeChildNode.nextElementSibling" , "nextElementSibling")}} properties has been removed from {{domxref("DocumentType")}}, because of compatibility problems ({{bug(932501)}}).</li>
</ul>

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

<ul>
 <li>Support of <span id="summary_alias_container"><span id="short_desc_nonedit_display">the </span></span><code>mathvariant</code> attribute has been added ({{bug("114365")}}).</li>
</ul>

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

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

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

<ul>
 <li><span id="summary_alias_container"><span id="short_desc_nonedit_display">Opus in WebM</span></span> is now supported ({{bug("887978")}}).</li>
 <li><span id="summary_alias_container"><span id="short_desc_nonedit_display">The VP9 video decoder</span></span> is now supported ({{bug("833023")}}).</li>
</ul>

<h3 id="Network">Network</h3>

<ul>
 <li>Support of <code>SPDY/2</code> has been removed.</li>
</ul>

<h2 id="Changes_for_addon_and_Mozilla_developers">Changes for addon and Mozilla developers</h2>

<ul>
 <li>The interface of <a href="/en-US/docs/Mozilla/JavaScript_code_modules/DeferredTask.jsm">DeferredTask.jsm</a> has been changed, and the <code>isPending()</code>, <code>start()</code>, <code>flush()</code>, and <code>cancel()</code> methods have been removed ({{bug("940408")}}).</li>
</ul>

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

<ul>
 <li>CSP was not enforced in sandboxed iframes. This has been fixed ({{bug(886164)}}).</li>
 <li>The CSP 1.1 experimental <code>script-nonce</code> directive has been implemented. The preference <code>security.csp.experimentalEnabled</code> should be set to <code>true</code> to enable this functionality ({{bug(855326)}}).</li>
</ul>

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

<ul>
 <li><a href="https://www.fxsitecompat.com/en-US/versions/28/">Site Compatibility for Firefox 28</a></li>
</ul>

<h3 id="Older_versions">Older versions</h3>

<p>{{Firefox_for_developers('27')}}</p>