You will need to install a user script manager extension to install this script.
Please make sure you install the script from greasyfork.org, not fake sites.
AV1 is highly recommended for Windows 11 and MacOS users. Higher Quality and Lower Bandwidth is provided.
Opposite Script: Disable YouTube AV1
For Windows, you must have to install AV1 Video Extension. (edge/chrome/firefox/... etc)
Chrome: including Brave, Cent, etc
Important Note: Some 2K & 4K videos are still running with VP9 and no AV1 encoding is provided.
AV1 will be used over VP9 as possible. (Higher Quality & Higher Compression)
AV1 is not yet supported in hardware decoding.
VP9 is usually supported in hardware decoding in modern PC.