Google Drive Links URL format and query parameters

Question

I\'m desperately trying to find where the google drive and google docs urls scheme and query parameters are documented. For example what is the usp= parameter which seems to

Answer 1

/u/2/:

• u stands for user
• 2 denotes the third° user account you logged into – in the current browser (profile). That means that the same number can get associated with a different Google account in each browser (profile), if you first log in in a different order per browser (profile).
      ° 2+1 due to counting zero-based: The first account is /u/0/.

_{Source: my experience with Google Mail and Contacts}