Authentication

Authentication (auth) is how your application knows who is using it. When a user signs in with Google, enters an email and password, or clicks a magic link, they are authenticating: proving their identity so the app can show them the right data and permissions.

Modern auth is complex under the hood: secure password hashing, session tokens, refresh flows, OAuth handshakes with Google/GitHub, and email verification. This is why most teams use managed auth services like Supabase Auth, Clerk, Auth.js, or Firebase Auth instead of building from scratch.

For vibe coders, auth is one of the first "real" features you need when building any app with user accounts. The Modern Vibe Coding curriculum uses Supabase Auth because it integrates tightly with the database and supports multiple sign-in methods (email, Google, GitHub, magic links) out of the box.