How to make a file download only after subscribing to a channel?

Question

YouTube

Hello everyone, tell me, I saw it repeatedly on YouTube - in order to download a file, you must first subscribe to the channel, how can this be done?

Answer 1

1. The file is on the server.
   
2. The link leads to this server.
   
3. Going to the server starts an interaction with YouTube via the API to get the person's subscriptions .
   
4. If there is a subscription, the file is given for downloading.
   

Answer 2

https://www.youtube.com/watch?v=bnvWstQ0NEg