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How to install/enable codec for embedded mp4 video?

  • 3 replies
  • 6 have this problem
  • Last reply by cor-el

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An internal page at work (so unfortunately I can't share a link) just shows "A plugin is needed to display this content" instead of video content. Doing an "Inspect element" shows that the content is an mp4 video in an object tag.

I understand that Firefox should be able to play mp4 video, as long as I have the required codec:

I tried the Windows update files suggested here: but they would not install on my Windows 7 64-bit system (I get a message that they do not apply to my system).

On the same post, it suggested checking the values of and media.directshow.enabled in about:config. The first setting does not exist for me, and the second setting is enabled (set by default). Interestingly, the test site on that page works fine for me ( ).

Since the "supported media formats" page specifically mentions H264 encoded MP4 as needing a plugin, I checked my addons page for plugins that need enabling. All are enabled or set to "ask", but there is one plugin that seems relevant, that is permanently stuck on "will be installed shortly" status: the Cisco OpenH264 video codec.

Since this plugin seems like it might be relevant, I tried to find a way to force a manual installation. I tried setting the setting in about:config as suggested here, but that did not change any behavior as far as I can tell:

I tried downloading the zip file manually from and extracting to C:\Users\{myUserName}\appdata\Roaming\Mozilla\Firefox\Profiles\{idOfSomeKind}.default\gmp-gmpopenh264\1.1 as suggested here:

That did not work either. I did not understand the part about media.gmp-gmpopenh264.* prefs; none of those settings exist in my about:config except for media.gmp-gmpopenh264.autoupdate.

The media.gmp-gmpopenh264.provider.enabled option noted on does not exist.

In case it's not obvious, I did restart Firefox after every about:config change.

How can I convince Firefox to play embedded mp4 video? What plugin do I need and how do I install it, if I need one?

All Replies (3)

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An <embed> tag and an <object> tag always require a plugin. Firefox will only use the HTML5 media player if an <audio> or <video> tag is used. So it won't help to check the media prefs.

A possible workaround is a bookmarklet to convert the OBJECT to an AUDIO tag.

javascript:(function(){var cE='audio',eE=document.querySelectorAll('object,embed');for(i=0;E=eE[i];i++){N=document.createElement(cE);N.setAttribute('src',E.src||;N.setAttribute('controls','');N.setAttribute('autoplay','true');E.parentNode.replaceChild(N,E)}})()
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Thanks for that info! I may try the bookmarklet. If I went with a plugin instead would it be something like QuickTime or DivX I'd be looking for or is there a better option? Do these even work with the removal of NPAPI?

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Plugin will no longer work in Firefox if NPAPI support gets removed. Flash might still be supported somehow and there will likely also be a solution for Java. If the content type is supported in the HTML5 media player then that will always stay working.