JWT Authentication Tutorial
Understand JSON Web Tokens: how they are signed, issued, stored and checked, and where they go wrong
Intermediate4 lessonsabout 27 min of reading
This course is for developers who have copied a JWT login snippet from somewhere, or inherited one, and want to understand what it actually guarantees. You should be comfortable with basic HTTP (headers, status codes) and with reading short Node.js programs; if the HTTP part is new, start with REST API Development and come back.
You will take a real token apart and rebuild its signature with Node's crypto module, then build a small login service that issues short-lived access tokens and rotating refresh tokens. You will compare cookies and web storage by what each one exposes you to, and finish with a verifier that checks algorithm, issuer, audience and expiry, plus a plan for revoking tokens. The framing throughout is defensive: every risky pattern is shown next to the check that stops it.
The four lessons go in the order a real implementation grows: anatomy and signatures first, then the login flow, then storage in the browser, then expiry, revocation and review of the usual mistakes. Every program was run, and the outputs are real; where a value is random or time-dependent, the lesson says so. For the wider picture of web risks, the OWASP Top 10 and Cybersecurity Fundamentals courses are good companions.
JWT Authentication lessons
- 1JWT Explained: Structure, Signing and Verification with Node.jsDecode a real JWT, build and verify an HS256 signature with Node's crypto module, and learn what the header, payload and signature do and do not protect.6 min read
- 2JWT Login Flow: Access Tokens, Refresh Tokens and RotationBuild a JWT login service with short-lived access tokens, rotating refresh tokens and reuse detection, and read the real request and response output.7 min read
- 3Where to Store a JWT: HttpOnly Cookies vs localStorage ComparedCompare HttpOnly cookies, localStorage and in-memory storage for JWTs by what each exposes to XSS and CSRF, with a runnable cookie-based Node example.7 min read
- 4JWT Security: Expiry, Revocation and the Mistakes to AvoidVerify JWTs properly: pin the algorithm, check issuer, audience and expiry, plan revocation, and avoid secrets in the payload, with a tested verifier.7 min read
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