Many people (including yours truly) are annoyed by this change - not a browser issue, but a decision that YouTube made.

See : https://news.slashdot.org/story/18/07/28/0215215/for-better-or-worse-youtube-now-adapts-to-multiple-aspect-ratios

Also : https://gizmodo.com/for-better-or-worse-youtube-now-adapts-to-multiple-asp-1827936921

Looks like we'll have to put with it .......  :(

In addition :

'Thought it over (and checked some more videos) and I've come to realize that those videos that appear to be smaller now, really are not : Before, when those white spaces on both sides were black, we only had the illusion that the video screen was bigger, but it really wasn't.

We'll get used to it ..... (although the black rectangles were easier on the eyes)

I thought that it was a change by youtube, but this does not occur on other browsers. If I watch an affected video in chrome for example, it will look like it did before with the black bars on the side, but have the different size in firefox. Why would this be?

izektor said

I thought that it was a change by youtube, but this does not occur on other browsers. If I watch an affected video in chrome for example, it will look like it did before with the black bars on the side, but have the different size in firefox. Why would this be?

That's remarkable, cause I experience the same change in other browsers.

It is not a browser issue - it's a change that was made by YouTube.

Did you not read the articles I gave you links to  ?

I did read them, I was just confused as to why it would not be happening in my other browsers

izektor said

I did read them, I was just confused as to why it would not be happening in my other browsers

Maybe you haven't played videos (yet) where this applies to when you're using other browsers - it doesn't affect every video.

Like I said : I experience the same annoying change, no matter which browser I use.

Not a Firefox issue , but a decision, made by YouTube .....

I understand now that it is not a firefox issue.

And I checked a video that had changed in firefox in chrome and it did not change, weird. Well, all I can do is hope that Google has mercy and at least lets us roll it back individually. And I HATE using chrome so that isn't a viable option.

Thanks for your quick replies, have a nice day.

izektor said

Thanks for your quick replies, have a nice day.

My pleasure - I hope you'll have a nice day too  !

BTW : I just saw many comments on YouTube where people are complaining about this issue .....

See also:

• https://productforums.google.com/forum/#!topic/youtube/5QyTjyT-IZo

I think I am going to use theater mode now