On some other sites, I get this information: "Video format or MIME type is not supported". Please, help.

You are probably out of luck on Windows XP to play H.264 encoded MP4 files in Firefox. There is only support to play MP3 files.

See this forum thread;

• [/questions/1053509] MP4 files won´t play

You will probably have to install Google Chrome as long as that is possible on Windows XP to play MP4 files. Otherwise you would have to paste the location of the file in a media player like VLC that is capable to play such files.

Crap, that's not so good. I don't like Chrome, it has dreadful UI and many youtube videos won't play for me (60fps in HD). IE 8 is even worse than Firefox. New OS is expensive.

I don't really understand Vine... On Windows 7 with nothing disabled, I get a video tag with this src attribute. If you paste copy/paste this into the address bar and press Enter, does it play?

blob:https://vine.co/891440a8-491e-43ce-86c4-1423f089a996

For me, it works with blob at the beginning and not without it. This could be a post-XP thing.

Could you try this old workaround: click the faint stack of 3 dots above the video "poster" image and choose Embed. This should open that particular video's page with the embed viewer overlaid. This viewer uses an older syntax (doesn't use blob) that hopefully will still work in XP.

But... the extra steps are a hassle so hopefully another workaround will be found.

"blob" doesn't work, Firefox doesn't recognize it and I just cannot go there (FF ignores "enter").

Embed preview doesn't work as well. There are more details popping out on the picture (like sound on/off, uploader's profile, vine's title) but the clip still won't play.

Suprisingly, Vines started working affter updating my browser to FF 38.0.5.