Overview

JWT Course

Learn JSON Web Tokens from structure to claims, verification boundaries, and practical debugging.

This course teaches JSON Web Tokens as an authentication and authorization format. It is not a button-by-button walkthrough of a decoder. You will learn what is inside a JWT, which claims matter, and why decoding a token is different from trusting it.

Who this course is for

  • Frontend and backend developers debugging Authorization: Bearer ... requests
  • Engineers working with OAuth, OpenID Connect, API gateways, or session migration
  • Anyone who has decoded a token and wondered whether the result is safe to trust

What you will learn

  1. The compact three-part JWT structure
  2. Header fields such as alg and typ
  3. Registered claims such as exp, iat, nbf, iss, aud, and sub
  4. Why decode is not verify
  5. Common validation mistakes and debugging patterns

Use the related JWT Decoder to inspect examples after each lesson, but keep the main idea in mind: decoded claims are readable, not automatically trustworthy.

Start lesson 1
Common URL Encoding Bugs in OAuth RedirectsOAuth redirect bugs often come from double encoding, missing encoding, and confusing query strings with nested URLs.JWT Decode vs Verify: What Developers Should CheckDecode a JWT to inspect claims, but verify the signature and trust rules before using it for authorization.JWT vs Session AuthenticationCompare JWT-based authentication and server-side sessions for web apps, APIs, revocation, scalability, and debugging.