Introduction to authentication and explaining the difference between authentication and authorization as this is something that many people confuse.
HTTP Status codes also help you show if a user is unauthenticated or unauthorized. These come from using 401 Unauthorized and 403 Forbidden HTTP Status codes, however, they are a little misleading. 401 Unauthorized actually means the user is not authenticated while 403 Forbidden means the user is not authorized to perform the action they are trying to do.
Understanding 403 Forbidden
Course: HTTP Basics
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