Mahfuj Alam
JSON Web Tokens are everywhere, but most implementations have critical security flaws. Learn the right way to implement JWT auth with refresh tokens, secure storage, and token rotation.
JSON Web Tokens are widely used for authentication, but improper implementation leads to serious security vulnerabilities.
Never store JWTs in localStorage — it's vulnerable to XSS attacks. Use httpOnly cookies for refresh tokens and keep access tokens in memory.
Access tokens should have short expiry (15 minutes). Use refresh tokens for issuing new access tokens without requiring re-login.
const accessToken = jwt.sign(
{ userId: user.id },
process.env.JWT_SECRET!,
{ expiresIn: '15m' }
);
Implement refresh token rotation — when a refresh token is used, invalidate it and issue a new one. This helps detect token theft.
JWT security requires careful attention to token storage, expiry, and rotation strategies. Following these practices will significantly improve your application's security posture.
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The refresh token rotation section saved me from a huge security mistake.
Finally a practical guide that doesn't just say 'use httpOnly cookies' without explaining why.