JWT Security Best Practices

JSON Web Tokens (JWT) are the standard for modern web authentication, but misconfiguration can lead to complete account takeover. Learn how to secure your tokens in 2026.

1. The Risk of LocalStorage

Many developers store JWTs in localStorage because it's convenient. However, localStorage is vulnerable to Cross-Site Scripting (XSS). If an attacker injects a script into your page, they can read your tokens instantly.

Recommendation: Use HttpOnly cookies for token storage. They are inaccessible to JavaScript, mitigating the risk of token theft via XSS.

2. Token Expiration Guidance

Short-lived tokens are safer. If a token is stolen, a short expiration limits the window of opportunity for an attacker.

• Access Tokens: 15 minutes to 1 hour.
• Refresh Tokens: 7 days to 30 days (stored in a secure database for revocation).

3. Common Attack Vectors

• Algorithm Switching: Attackers changing alg: HS256 to alg: none. Always explicitly verify the algorithm on your server.
• CSRF: If using cookies, ensure SameSite=Strict or Lax is enabled to prevent Cross-Site Request Forgery.
• Secret Strength: Use a high-entropy secret key (at least 256-bit) to prevent brute-force attacks on the signature.