A work around is to download the clip, and use your other programs to watch it. Adobe players do not play everything.

You wrote,

Client said that video cannot load on firefox except other browsers. It shows "Video format or MIME type is not supported". Firefox version is 33.0.3. Video is mp4 format.

Who is the "client" and what is the client's operating system ... also Windows 7 or something else? What media players or plugins are installed?

Could you post a link to a video that shows the error "Video format or MIME type is not supported"?

Related information:

• Fix common audio and video issues
• Audio and video files in Firefox

P.S. In case it helps, here are some mp4 video tests you can try (from mozillaZine's Testing plugins article) to see if they work for you in Firefox 33. (They both work fine for me on Windows 7 without needing a plugin.)

• http://www.html5videoplayer.net/html5video/mp4-h-264-video-test/
• http://techslides.com/demos/sample-videos/small.mp4

See also:

• https://developer.mozilla.org/en-US/docs/Web/HTML/Supported_media_formats

myatyee91,

Are you still looking for a solution to the "Video format or MIME type is not supported" error?

In case it helps:

I found a related bug report indicating that problem videos were being served with a wrong "octet-stream" MIME type instead of the correct "video/mp4" type. _{(Please see Bugzilla Etiquette before commenting in bug reports)}

• Bug 975809 - Video format or MIME type is not supported. - should do content sniffing on video tag

I also found answers from previous questions with other solutions:

• /questions/1011225#answer-604988 (download Media Feature Pack for N and KN versions of Windows 8.1)
• /questions/1024630#answer-639230 (reset Firefox preferences or else disable conflicting Firefox extensions)

Hello Everyone,

I thanks and appreciate for all of your suggestions. I resolved the problem that I posted. Actually, this error does not show on my firefox browser, shows on client's firefox only. To solve this problem, I also uploaded .webm format video type to support firefox browser that cannot play .mp4 format. Well Done Guys! Sorry for late reply.

Best Regards, Myat

Thanks for posting back with the outcome, Myat. I marked your reply as the solution.