What is Token Security?
Best practices for creating, storing, transmitting, and invalidating the tokens (JWTs, API keys, session tokens) that control access to your application and its data.
In plain English
Tokens are like digital hall passes. A well-designed hall pass specifies who it's for, where they can go, and when it expires. Token security ensures these passes can't be forged, stolen, or used beyond their intended scope.
How it works
Tokens are strings that represent a user's identity or permissions. JWTs encode claims (user ID, role, expiration) and are cryptographically signed to prevent tampering. Access tokens grant short-lived access (15 minutes), while refresh tokens allow obtaining new access tokens without re-logging in. Proper token security covers the entire lifecycle: generation, storage, transmission, validation, and revocation.
Why it matters for AI-built apps
AI tools frequently generate tokens with poor security defaults — long or no expiration, weak signing secrets, storage in localStorage (vulnerable to XSS), and no refresh token rotation. A compromised token gives an attacker complete access to a user's account. Token security is the foundation of your authentication system.
Common issues
Tokens that never expire, storing tokens in localStorage instead of httpOnly cookies, using weak or hardcoded signing secrets, not validating token signatures on every request, missing refresh token rotation (allowing stolen refresh tokens to work indefinitely), and including sensitive data in JWT payloads (which are base64-encoded, not encrypted).
Best practices
Keep access tokens short-lived (15 minutes). Store tokens in httpOnly, secure, sameSite cookies. Use strong, randomly generated signing secrets stored in environment variables. Implement refresh token rotation. Validate signatures on every request. Don't store sensitive data in JWT payloads. Implement token revocation for logout and password changes. Use asymmetric signing (RS256) for distributed systems.
Frequently asked questions
Why shouldn't I store JWTs in localStorage?
localStorage is accessible to any JavaScript running on your page. If your app has an XSS vulnerability (even in a third-party script), an attacker can read the token and impersonate the user from anywhere. httpOnly cookies can't be accessed by JavaScript, making them immune to XSS token theft.
How short should my access token lifetime be?
15 minutes is a common and secure default for access tokens. Pair them with refresh tokens (valid for days or weeks) that rotate on each use. This limits the damage window if an access token is stolen, while keeping the user experience smooth by avoiding frequent re-logins.
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