This is an option set in the browser, so it would not effect your other browsers. To change it, go to youtube.com, select a movie you would like to watch, then click the gear icon at the bottom. It will then show the current settings for speed and quality of the movie. To change the setting, simply click the "360p" and it will then give you the other definition options. See screenshot if these directions do not make sense.

Have a great day!!

Jon

I know that ... But I ve got another problem ... the problem is that when I am opening youtube on chrome for example my default its 480p and lager player size . So that means that is something wrong with my firefox browser. You can see the difference in the screenshots .

The thing is that yesterday my youtube videos were played like the video on chrome browser and today I got it smaller like the screenshot on mozila . Thanks for the answer

So your default won't change with the fix that I gave you?

No . The thing is that I can change the quality and that isnt a problem , but the problem is that the video size is not changing all the time the size stays like 360p . do you understand me ?

So you get a bigger frame but the video in it is the same size? I think that depends on the video. I see that sometimes. The newer videos are larger, but the older ones are smaller.

Noup could you see the difference on the first and the second picture ? its the same video on the same laptop but only different browsers . So def I have problems with mozila not youtube ....