¡Hola Elanti!

Are you using the HTML5 player? You can check at https://www.youtube.com/html5

Right click on the video then click "Report playback issue".

Let us know if this helps.

¡Gracias!

Some other useful resources:

• https://support.google.com/youtube/checklist/3480866
• https://support.google.com/youtube/answer/6013340

That was the problem. It seems I was using Flash. I don't know how could that happen, I didn't touch anything. Back to HTML5 and everything back to normal. Thank you so much!!

Glad to hear it's working =)

Remember to http://occupyflash.org/ ;-)

On Windows XP there is normally much more chance for issues with the HTML5 media player because there is no native support for playing MP4 files. A Flash player should support all available formats unless there is a problem with the Flash plugin or with a content blocking extension.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

cor-el said

On Windows XP there is normally much more chance for issues with the HTML5 media player because there is no native support for playing MP4 files. A Flash player should support all available formats unless there is a problem with the Flash plugin or with a content blocking extension.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

I just tried restarting Firefox in Safe Mode, and my problem with Flash persists: only 144p available. I also confirmed that I have the latest version of Flash installed. Since I'm not planning on changing my computer or my operating system (they're working just fine), I guess I'm going to stick to HTML5, and (regrettably) I'm going to switch to Chrome whenever I need to watch a video on HD.