Hi there! You can try it combined with 'force theater mode' (right below Player Size, so that it won't go to the small player)
Alternatively please disable general: 'limit page width', so there is more space + Player Size 'Full page'

https://github.com/code4charity/YouTube-Extension/issues/1204

EDIT2: ah! hey, probably the autoplay setting! (i couldn't reproduce either in the latest Firefox. But it was reported 3 times by now)
https://github.com/code-for-charity/YouTube-Extension/issues/1213 ( The other setting is new and could also be called "Unlimited page width" to be more intuitive. (even though technically it is something that Youtube visually does by default already and we just switch it off. We can always improve and make the most important features bigger and label some others as rare/specific. But this is an avid task and not trivial and should not be required to avoid low ratings ( https://github.com/code4charity/YouTube-Extension/discussions/748 )

- this project is actually is the only existing solution for many things and the most convenient one too in comparision. Most settings allow to see the effect instantly on the current page, unlike all alternatives, that require to make settings in different tabs. (- yet 'youtube enhancer' & 'magic actions for youtube' do have a million more users still) - and bad ratings might make the gap bigger if anything.

(To be more precise, the width limit feature is meant to allow the site/video to expand to the sides. This means, if you have a superwide screen or also hide related videos, then the video height wont fit fully, unless you also hide the youtube header, or zoom or use auto-fullscreen. We are not a one-fit-all solution by definition for a billion users like YouTube itself. We volunteer to serve specific wishes. Most users are willing to experiment for some minutes for once. In a 100 features a few will in fact naturally not help you. All of which we can try to label perfectly in the next update, but never avoid completely, by nature of even having more than a few features. You can still refer to your list of 'activiated Features' (and currently this feature only appears once you disabled the button.) (You can also reset our settings to go back to YouTube defaults.) Anything could be labeled or come with an alert, but thats also complification in the eyes of other users. (You don't need to click a button unless it makes sense to you.)

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EDIT: Thanks, tough luck* - Almost there though! (*this confirms it is a rare bug. However we will be happy to fix it for you in time!) - Did you notice the last 4 Versions are all within a few days?😊 - If you go back a step further (3.223 or 3.899), then it works most-likely and you will have discover easily, at what version the bug starts🤩. (Finally, you probably have a rare computer or system? (and can see whats happening in the browser console?) bugs@improvedtube.com. BTW you can quickly try an extension in a private tab, with no other extension running just to make sure) -----------------
hi, thanks. Please understand some bugs are rare and bad luck. The bigger a project is, the less likely you run into any, but it can't be excluded completely. To find it fastest you might need to report more details ( https://github.com/code4charity/YouTube-Extension/issues ). Also likely it just started yeserday and was not there in the prevous versions, which you can still get. Many Features: Yes, browser extensions are unfortunately supposed/presented to be small/single-purpose. Still we are providing a 100 of the most wished and requested features without 100 times more success than easy extensions. This is also much more teditious than making our own site which would be fun/need no maintenance. We are volunteers working hard. Youtube has a billion times more money than us. So you might not want to give 1 star, to support the cause getting anywhere near as much visiblity, as it deserves (and consequently even faster fixes) Many smiles!

we are at it. (not every bug happens to everyone.)

thanks! 1. oh, of course added stop to the list of player/on-page buttons! https://github.com/code4charity/YouTube-Extension/issues/842#issuecomment-809077449 2. buffering in advance is critical. please join us & add your details. Just wrote the long answer for you here: https://github.com/code4charity/YouTube-Extension/issues/581#issuecomment-1014280878 --- Please keep in mind it can be so frustrating, if not wrong to pressure us based on the one feature you grew fond of years ago, which we have not, which might be for a good reason. You might want to give 5 stars to support the cause rather than making it seem impossible for us to get 5 stars and get anywhere near as much visiblity as our work deserves. ----Browser extensions are unfortunately supposed/presented to be small/single-purpose. We still are avidly providing a 100 of the most wished and requested features without 100 times more success than easy extensions. This is many times more teditious than making our own site which would be fun/need no maintenance. We are volunteers. Youtube has a billion times more money than us. Many smiles!

❤

edit: please keep your promise
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hi, you 1. click the 'Improve Youtube!' (extension icon, top right of browser),
2. 'Player' 3. 'Rotate' (you will find a new button in the youtube player)
-2. Alternatively you can just Type 'Rot to enable the feature
( please understand we are hardworking volunteers and blackmailing with one star rating is not right. There should be big reason. It can frustrate us for a long time. Even with 4 stars the pressure is real.)
many smiles