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There is a limit of active (valid) access tokens and it is 5 access tokens per user per app at the same time. This means that a user can logins to use the same app on 5 different computers. If he/she logins the same app on the 6th computer, one of the access token for the app on a computer he logged in earlier (most probably the first one) will be revoked.

There is no such limitation of token generation bu OAuth server.

There is only rate limit of applied to prevent unwanted attack on server.

x-rate-limit-limit →5 which means 5 OAuth Calls per min per extension .

There is no other limitation