If you spend enough time on Youtube, you start noticing little annoyances and things that you would like to change or play around with, but the provided Settings are generally not flexible enough to satisfy your needs. Luckily, there are tons of free extensions for Youtube that let you customize your viewing experience and even turn it into something cinema-like.
Always Open in HD
The thing I, personally, find quite annoying is that Youtube doesn't let you set HD quality as the default value for every video you open. You can only choose to open videos in the highest possible quality Youtube sees fit after it looks at your bandwidth and calculates whether it will be able to deliver the content to you fast enough to not make you wait every 5 seconds. Well-intentioned, but poorly implemented in my personal experience: my Internet connection is fast enough to play videos in high definition, which is something I know for a fact, because when I switch a video to the best quality (which I have to do in 90% of the time), it loads perfectly. Enough with the complaining, let's get to the solutions available on Chrome Web Store.
Extensions to always play videos in HD or choose the default quality on Youtube:
Don't want to see what trolls have to say about your favorite artist? Not a problem with these extensions, simply choose to hide comments automatically:
A different approach is implemented in Herp Derp for Youtube, you will still see the comments, however, randomly replaced with combinations of herps and derps for your amusement.
You can also choose to pause the videos you open by default, which is also one of the most annoying things in Youtube, especially if you like to open a bunch of videos in separate tabs.
Pause Video when you leave the tab: Smart Pause for Youtube (resumes when you come back).
Put Videos on Repeat
Liked a video and want to watch it on repeat for a while without having to press anything every time it ends?
The Ultimate Free Package
If you want to install a single extension that would let you tweak everything from a single interface: take a look at Magic Actions for Youtube. The list of features is pretty extensive and includes the AutoHD feature, the ability to quickly take screenshots, the Stop Autoplay feature, the option to hide comments, Replay, and much more.
Check out Magic Actions for Youtube on Chrome Web Store.