I want to get a user id / Google id from a app user without Google sign in. Is it possible to identify a user without authentication?

I want to sync data between devices without a login.

Thank you for any tips like classes or anything else.

CodePudding user response：

Is it possible to identify a user without authentication?

No. Identifying a user is basically the literal definition of "authentication". It's like asking if you can get wet without using a liquid.