Hi   !

As you're on Windows XP   -   you could try this add-on :

https://addons.mozilla.org/en-US/firefox/addon/youtube-flash-player/

You don't have any Flash blocking extensions, do you  ?

I have tried it. but its not working. Also no flash blocking extensions

SinzJ said

I have tried it. but its not working. Also no flash blocking extensions

Bummer   ! Could you try this test page, please :   https://www.youtube.com/html5

Stab in the dark :   if you have any YouTube related add-ons, would you disable them and see if that makes a difference  ?

No. Its not working

I believe the problem can also come from XP being so old and not supported, that video support is just being phased out, not 100% on that though. And also because XP isn't updated anymore to support new video format standards. When did this problem start?

Firefox relies on built-in OS support to play (MP4) media files via the HTML5 media player. On the Windows XP platform you do not have native support for playing MP4 files with the HTML5 media player.

You can try if the solution posted here to add support for playing MP4 files works for you.

• http://www.msfn.org/board/topic/175591-enable-mp4-h264-aac-html5-video-in-firefox-on-windows-xp-without-flash/

this started when i updated flash payer. Until now i was using the addon youtube flash player & it was working fine but after updating flash i can't watch videos in flash player & some videos aren't playing. This started around 4 days back.

Also i am able to watch the same videos (that aren't playing now) after 1 or 2 days in HTML5 player.

There are reports from the last view days that YouTube has stopped supporting the Shockwave Flash plugin and only works with the HTML5 media player. So on Windows XP you can no longer use the Flash player and would have to use a workaround like I posted above.

Hi SinzJ, please disable or remove your YouTube Flash Player extension, since it is now obsolete, to make sure it is not interfering with YouTube.

Another XP user observed that he has problems with newer videos on YouTube, and my speculation is that is because the person who uploaded the video used an MPEG format that Firefox on Windows XP normally cannot decode.* Eventually, YouTube should generate the other formats which CAN play in Windows XP, but it takes time. If you see that same pattern, that the problem is limited to the newest videos, I think it's just how it is for now.

The link in cor-el's earlier post is about a way for Firefox to decode MPEG videos even on Windows XP, so you may want to check that out: https://support.mozilla.org/questions/1169510#answer-991498

* On Windows, Firefox uses Media Foundation to decode H.264/MP4 videos. Microsoft released Media Foundation for Vista, 7, 8, etc., but never made it available for XP.

Thank u for your reply. I'll try it

Thank u for your reply. I'll try it

try it, it works. Since you're on the newest Firefox, you'll need to create a new entry in the about:config:

media.gmp-eme-adobe.forceSupported

Set it to true.