Authentication in MERN Apps: JWT, bcrypt, Redis, and OAuth2

Authentication in MERN Apps: JWT, bcrypt, Redis, and OAuth2 Most web app breaches trace back to one failure: weak authentication. In 2023, the MOVEit Transfer breach exposed 60 million records, partly because session tokens were predictable and revocation was nonexistent. This guide walks you through building auth that holds up in production. 1. Authentication vs. Authorization Authentication answers one question: Who are you? Authorization answers a different question: what are you allowed to do? They are separate systems that work in sequence. A user authenticates with an email and password. The server returns a token. That token then determines authorization: which routes the user accesses, which data they read, and which actions they perform. Definition: Authentication The process of verifying an identity claim. You say you are [email protected]. The server confirms or denies it. Definition: Authorization The process of checking permissions after identi