Use when migrating or switching from an existing auth provider (Firebase, Cognito, Supabase, Clerk, custom auth) to Auth0 - covers bulk user import, gradual migration strategies, code migration patterns, and JWT validation updates.

Add authentication and authorization to an app — login, signup, session management, and protected routes. Supports Auth0, NextAuth, Clerk, Supabase Auth, and custom JWT. Use when the user says "add login", "protect this route", "add auth", or "users need accounts".