What happens when you try?

Flash Player Test Page
YouTube Test Page: What video does this browser support

FredMcD said

What happens when you try? Flash Player Test Page


It says "You have version 20,0,0,267 installed."

YouTube Test Page: What video does this browser support

It says these have blue check mark

HTMLVideoElement WebM VP8 Media Source Extensions MSE & WebM VP9

It says these have red exclamation mark:

H.264 MSE & H.264

My browser says it has OpenH264 Video Codec provided by Cisco Systems, Inc. 1.5.3 - and is always active

There have been many times I get the same message. Funny thing. When I download the clip, it plays just fine in my players.

My browser says it has OpenH264 Video Codec provided by Cisco Systems, Inc. 1.5.3 - and is always active

That is not used for multimedia playback. It's in Firefox for the Hello feature, for WebRTC use.

Overall, you really need to think about upgrading to Windows 7, at least. Or switch to a Linux operating system on an old PC. I would be surprised if Firefox support for WinXP continued to the end of 2016.

Windows XP doesn't include support for playing H.264 encoded MP4 videos, so you wont be able to use the HTML5 media player to see such videos.

You can set these prefs to false on the about:config page to disable the HTML5 media player to see if the website switches to a Flash based player.

• media.windows-media-foundation.enabled
• media.directshow.enabled

You can open the about:config page via the location/address bar. You can accept the warning and click "I'll be careful" to continue.

• http://kb.mozillazine.org/about:config

cor-el said

Windows XP doesn't include support.....

• media.windows-media-foundation.enabled

--does not exist in my about:config

• media.directshow.enabled

--exists but toggling has no change to problem