Firefox 4 Beta Does not Play Local WebM Videos




7 years ago
7 years ago


(Reporter: Baris Derin, Unassigned)


(Depends on: 1 bug)

Windows XP
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(Not tracked)


(Whiteboard: [fx4-unco-bugday] [fixed by Bug 641102])



7 years ago
User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv: Gecko/20101026 Firefox/3.6.12
Build Identifier: Mozilla/5.0 (Windows NT 5.1; rv:2.0b6) Gecko/20100101 Firefox/4.0b6

Firefox 4 Beta does not play Local WebM video files. The recent security changes about local URIs broken the WebM playback for local files. If possible, playback for local WebM files should be re-enabled.

Reproducible: Always

Steps to Reproduce:
1.Download the WebM file from:
2. Drag the AudioAPI.webm into Firefox 4 Beta
3. Simply it does not play the file but offers a download dialog.
Actual Results:  
Simply Firefox 4 does not play the file but offers a download dialog.

Expected Results:  
Simply Firefox 4 does not play the file but offers a download dialog. Firefox 4 used to play the local webm file inside the browser. Even 


preference change does not help. WebM is a innovative technology and has potential. Firefox should provide the users local webm playback option without breaking local security issues. I tried to create a Firefox add-on for playing local WebM videos but could not proceed because of this restriction.

Comment 1

7 years ago
Mozilla/5.0 (Windows NT 5.1; rv:2.0b8pre) Gecko/20101108 Firefox/4.0b8pre ID:20101108043306
>3. Simply it does not play the file but offers a download dialog.
That is not a security problem at all.
You have a content-type problem, the content type isn't correctly detected.
In most cases you have the wrong content-type for .webm saved as helper application or your windows registry returns the wrong content-type for this file extension.

Please try a new profile
moving to video/audio, shouldn't we "register" Gecko as handler for the .webm file extension ?
Component: General → Video/Audio
Product: Firefox → Core
QA Contact: general →
Version: unspecified → Trunk
Baris, do you still see this problem on the latest nightly? I cannot reproduce the problem on this specific URL. There are problems other webm videos. See bug 616252.

Comment 4

7 years ago
I am not sure still but high probably K-Lite Mega Codec Pack is overwriting the registry entries of Windows and the webm video privileges are taken from Firefox as Matthias described. And as Matthias suggested, the Firefox should play the webm files even Firefox is not registered as an handler for webm videos.

K-Lite Codec Pack is a video codec bundle and it is frequently used by Windows users. 

Download page for K-Lite Codec Pack:

Comment 5

7 years ago
I can confirm it is because of K-Lite. It takes the ownership for webm. But Firefox should still play webm files in browser.

Comment 6

7 years ago
The problem is still there in the latest beta 4.0b11
Depends on: 634945

Comment 7

7 years ago
Even if K-Lite takes the ownership for WEBM, Firefox should still be able to play the files. The capability of playing WEBM videos is already built into the Firefox 4.

Comment 8

7 years ago
I can confirm this issue exists with Mozilla/5.0 (Windows NT 6.1; WOW64; rv:2.0) Gecko/20100101 Firefox/4.0 and K-Lite 7.04 installed.
Ever confirmed: true
Whiteboard: [fx4-unco-bugday]

Comment 9

7 years ago
I cannot confirm this in Windows 7 and  Mozilla/5.0 (Windows NT 6.1; rv:2.0) Gecko/20100101 Firefox/4.0 with the K-Lite Codec Pack installed. The video plays but it doesn't show the controls. Changing to Full Screen the controls show.
I also confirm this.  Installed K-Lite.
Mozilla/5.0 (Windows NT 6.1; rv:2.0) Gecko/20100101 Firefox/4.0
No longer depends on: 634945
Depends on: 645288
Depends on: 634945
Please look in the windows registry and tell me if there is a content/mime-type registered for webm and which one ?
It's possible that the K-Lite codec pack changes that entry.
This is now fixed on trunk by the landing of bug 641102.
Depends on: 641102

Comment 13

7 years ago

Windows Vista 32-bit.
Build identifier: Mozilla/5.0 (Windows NT 6.0; rv:2.2a1pre) Gecko/20110331 Firefox/4.2a1pre
Last Resolved: 7 years ago
Resolution: --- → FIXED
Whiteboard: [fx4-unco-bugday] → [fx4-unco-bugday] [fixed by Bug 641102]
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