Please note that Twitter no longer uses the Flash Player for videos. Like many websites, they have moved to the newer HTML5 video player. This is the same technology used by YouTube.

Please navigate to the YouTube HTML5 information page and let us know which formats do not display a check mark.

Thanks.

These do not have a check mark. H.264 WebM VP8 How ever H.264 is installed as Plugin.

Correction: I Have disable all Flash Down Loaders and Flash Player addons and now all are checked. But I still can't play videos in Twitter.

Does that help with Twitter, too?

No that did not work.

Shot in the dark,   see if there are updates for your graphics
drivers:   http://mzl.la/1xKsEca

I believe that Twitter uses the H.264 codec, so we need to figure out why that is not enabled on your system. This should display a check mark on YouTube, even if the Cisco plugin is not installed or active.

Please check some hidden settings for me:

1. Enter about:config in the Firefox address bar
2. Bypass the warning message
3. Ensure that the following preferences have a value of true:
   • media.mediasource.enabled
   • media.mediasource.mp4.enabled
   • media.mediasource.webm.audio.enabled
   • media.mediasource.webm.enabled

Warning: You may need to restart Firefox for the changes to take effect.

I did all the thing recommended on that page. Updated drivers from computer manufacture, checked and installed all MS updates, turned off hardware acceleration and switched webgl.disabled to false. Videos still do not play in Firefox. As I said earlier. This problem arose about a month and a half ago and videos run fine in both MS IE and Chrome.

RE: about:config Search media.media all were set to true prior to search, so no change occurred and problem still exists. media.mediasource.enabled media.mediasource.format-reader media.mediasource.format-reader.mp4 media.mediasource.mp4.enabled media.mediasource.webm. enabled media.mediasource.whitelist

Another shot in the dark:

See:   'Fix video and audio playback problems on Firefox for Windows'

    http://mzl.la/1zLUDHu

You might need the media features pack linked in that last article if your Windows 8.1 is an unbundled N or KN version.

Otherwise, my question is:

If YouTube's HTML5 page says your Firefox can play MP4 video, why isn't it working on Twitter?

To see whether this is a general problem, could you try the test video on the following page -- ignore the table at the top, which is not live / not you, and scroll down to the first player labeled "H.264/MP4" -- does that video work?

http://www.quirksmode.org/html5/tests/video.html

If that works, it could be a problem specific to how Twitter is serving videos, which is sending a .m3u8 file full of various addresses to load instead of sending a full MP4 video.

I've seen 'Fix video and audio playback problems on Firefox for Windows' before and it does not apply.

From what I've read online is that Firefox does not internally support AVC/H.264. I don't know if this is true but the problem definitely reside with Firefox.

What about, media.hardware-video-decoding.failed being set to false?

My version is not Windows 8.1 unbundled N or KN version.

All the videos on the test page run fine. My problem is with videos in Twitter.

Twitter actually does some unique things. I used Firefox's Network Console to check on that, and there was an unfamiliar content type for their videos, mp2t instead of mp4. (Screenshot attached.) It plays on my Windows 7, so I don't think it's something that only works on newer versions of Windows.

If you want to see whether your Firefox is even retrieving those files, you can open the Network Monitor in the lower part of a Twitter tab using either:

• Ctrl+Shift+q (if not intercepted by the page or an add-on)
• Ctrl+Shift+k then click Network along the top bar
• menu button > Developer > Network
• (menu bar) Tools > Web Developer > Network

Then reload the Twitter page and the monitor should start filling with requests. You may need to scroll the top part of the tab to get to the video, then look for the M3U8 requests and see whether Firefox extracts out the .ts addresses and requests those.

If this is not a common problem with other users, could it be some about:config leftover from and addon? I see a lot of BOLD entries that are USER SET.especially for media.gmp-. Is there any way to reset the CONFIG to default? I tried a fresh reinstall after uninstalling Firefox and Flash Player and running a couple Registry cleaners and deleting the Profile. The fresh install did not write a new Profile and the new install would not run because it could not find the Profile.

RE: ' Firefox's Network Console' I found one *.m3u8 file from video.twitter.com. No *.ts listied.

As a side note, when I scroll down the page the video appears for a second and briefly runs for a millisecond before going black with the error message.

Hmm... could you check that line in the network monitor for a few things:

(1) Does the Type column show x-mpegURL ?

(2) If you click the line and then the Response panel, does it look something like this (telling Firefox to request additional .m3u8 files):

#EXTM3U #EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=320000,RESOLUTION=180x320,CODECS="mp4a.40.2,avc1.42001f" /ext_tw_video/779035755041656832/pu/pl/180x320/6Xnq_6z9mQw5YBYk.m3u8 #EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=832000,RESOLUTION=360x640,CODECS="mp4a.40.2,avc1.42001f" /ext_tw_video/779035755041656832/pu/pl/360x640/n7z-c6scOz7MOFpY.m3u8

Or like this (telling Firefox to retrieve .ts files):

#EXTM3U #EXT-X-VERSION:6 #EXT-X-MEDIA-SEQUENCE:0 #EXT-X-TARGETDURATION:3 #EXTINF:3.000, /ext_tw_video/779035755041656832/pu/vid/0/3000/180x320/hPHKeQRWZxIyeJIY.ts #EXTINF:2.267, /ext_tw_video/779035755041656832/pu/vid/3000/5267/180x320/-DsJluFrME5YLq8y.ts #EXT-X-ENDLIST

Nerd note: To paste text here that starts new lines with # and not have it turned into numbering, you need to surround the pasted text with

<nowiki>pasted text</nowiki>

Either way, I'm guessing your Firefox has a problem with M3U8 files, but I'm not sure what could cause that.

To try clean settings, you could do this:

New Profile Test

This takes about 3 minutes, plus the time to test Twitter.

Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.

Click the Create a New Profile button, then click Next. Assign a name like Sept2016, ignore the option to relocate the profile folder, and click the Finish button.

After creating the profile, scroll down to it and click the Set as default profile button below that profile, then scroll back up and click the Restart normally button.

Firefox should exit and then start up using the new profile, which will just look brand new.

Does Twitter video work any better in the new profile?

When you are done with the experiment, open the about:profiles page again, click the Set as default profile button for your normal profile, then click the Restart normally button to get back to it.

1. Network m3u8 file Response window is blank. No text. The file type is x-mpegURL

2. about:profiles does not do anything but produces an error message, "The address isn't valid" "The URL is not valid and cannot be loaded."

1artworkz said

2. about:profiles does not do anything but produces an error message, "The address isn't valid" "The URL is not valid and cannot be loaded."

Whoops, I thought you had Firefox 47. Now that I look closer, it seems to be Firefox 41. Why Firefox 41???

Here's the old way to create and switch among profiles:

Exit Firefox and start up in the Profile Manager using the Windows Run dialog (hold down Windows key and tap R) or the system search box -- type this and press Enter:

firefox.exe -P

Don't delete anything here!

Any time you want to switch profiles, exit Firefox and return to this dialog.

Click the Create Profile button, assign a name like Sept2016, and skip the option to relocate the profile folder. After creating the profile, select it and start Firefox in that profile.

Any difference?

When returning to the Profile Manager, you might be tempted to use the Delete Profile button. But... it's a bit too easy to accidentally delete your "real" profile, so I recommend resisting the temptation. If you do want to clean up later, I suggest making a backup of all your profiles first in case something were to go wrong.

I am using 41 because I tried 49 and I didn't like the New Tab feature The message said it was for security reasons. I didn't like the Default Home Page with all the tiles.

I fixed my problem with a completely clean install of Firefox. Now the videos in Twitter play fine as described here. https://support.mozilla.org/en-US/questions/1062472

I will add each of the extensions and test Twitter and post my findings here when I find the culprit.