YLooper by Tousif

Looper is a lightweight tool that lets you loop specific segments of any YouTube video. A custom, unobtrusive control panel is added directly into the native YouTube player controls. Simply type in your desired start and end times, or click the smart-set button to instantly capture the video's current timestamp. Toggle the loop icon, and the video will seamlessly repeat your chosen section. Perfect for learning music, studying lectures, or repeating your favorite moments."