How do offline videos on YouTube Web actually work?

Hey everyone,
I’ve been curious about something, YouTube lets you download videos for offline viewing on the mobile app, but now there’s also an option on the web (desktop browser) in some regions.

How does this actually work under the hood?

• Are the videos saved as encrypted files on your system?
• Can they be watched only inside the browser?
• Do they refresh/re-validate online after a few days like the mobile version?
• Where exactly are the files stored, and is the format accessible or completely locked?
• Is this similar to how Netflix offline downloads work?

Basically, I want to understand the technical side — caching, encryption, DRM, storage, etc.

If anyone has insights into how YouTube handles this on the web platform, please share! 🙏