Express

I’ve built OAuth authentication for 40+ Node.js apps. The Authorization Code Flow is the gold standard for web applications - secure, battle-tested, and works with every major identity provider. Here’s how to implement it right. Visual Overview: sequenceDiagram participant User participant App as Client App participant AuthServer as Authorization Server participant Resource as Resource Server User->>App: 1. Click Login App->>AuthServer: 2. Authorization Request AuthServer->>User: 3. Login Page User->>AuthServer: 4. Authenticate AuthServer->>App: 5. Authorization Code App->>AuthServer: 6. Exchange Code for Token AuthServer->>App: 7. Access Token + Refresh Token App->>Resource: 8. API Request with Token Resource->>App: 9. Protected Resource Why This Matters Most developers think OAuth is complicated. It’s not - if you understand the flow and avoid common mistakes. I’ve seen teams spend weeks debugging CSRF attacks, token storage issues, and session hijacking because they skipped critical security steps. ...