Greasy Fork

What am I missing?

I installed the script, edited it so const targetRes = "hd1080"; was const targetRes = "hd720"; (because I want videos to play in 720 instead of 1080), refreshed my Youtube vid (which is in theater mode), and it streamed in 1080.

1080, 4k, @60fps, etc, are usually overkill for me and I'd rather the video load fast at 720. Is there any way to do that with this script?

That should work. When you make that change you should only need to refresh the page to load the new setting (note that navigating to a different video on the youtube website doesn't actually cause a refresh since youtube loads everything dynamically on the same page).

I would try to edit the script again and set DEBUG to true. After that, look to see what is being logged in the browser javascript console (which can usually be accessed by pressing CTRL+SHIFT+I or CTRL+SHIFT+K). Then press the browser refresh button while on youtube. If you don't see anything being logged, then your script changes aren't being saved. If you do see something being logged, which resolution does it say it is available and trying to set it to? Have you changed the value of highFramerateTargetRes? If you are getting debug messages saying it is setting to 720 but it is still 1080, let me know what browser and user script manager you are using, and maybe an example video link, so I can investigate further.

Note that while the script will tell youtube to change the resolution as soon as possible after the video loads, youtube may try to initially load the video at a different resolution. If the initially loaded resolution is higher than the target, the script wont clear out the buffer (since it is higher quality and already downloaded), which means you may see it in 1080p when it has been set to 720p. But you wouldn't see that higher quality version for more than a second or so before it hits the 720p data, and youtube's quality selection would still say 720p.