Handle expired JWT tokens and refresh flows
JWT expiration errors occur when access tokens pass their expiry time and the application doesn't have proper token refresh logic. This causes authenticated requests to fail and users to be unexpectedly logged out.
Error messages you might see
TokenExpiredError: jwt expiredJsonWebTokenError: invalid tokenWhy this happens in AI-generated code
No token refresh mechanism implemented
AI-generated auth code creates JWTs but doesn't implement refresh token logic, so users are forced to re-authenticate whenever the short-lived access token expires.
Clock skew between client and server
AI tools set tight expiration times without accounting for clock differences between the server that issues the token and the server that validates it.
Refresh token stored insecurely or lost
AI-generated code stores refresh tokens in localStorage (vulnerable to XSS) or doesn't persist them at all, so the refresh flow fails and users must log in again.
How to fix it
Implement automatic token refresh
Use an HTTP interceptor (axios interceptor or fetch wrapper) that detects 401 responses, refreshes the access token using the refresh token, and retries the original request.
Store refresh tokens in httpOnly cookies
Move refresh tokens from localStorage to httpOnly, Secure, SameSite cookies. This prevents XSS attacks from stealing tokens and persists them across page reloads.
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Frequently asked questions
How long should JWT access tokens last?
Access tokens should be short-lived: 15-60 minutes is typical. Refresh tokens can last days to weeks. The short access token limits the window of abuse if a token is stolen.
Should I use JWTs or session-based auth?
JWTs are better for stateless APIs and microservices. Session-based auth (stored in a database) is simpler and more secure for traditional web apps. Many modern apps use JWTs with a server-side session store as a hybrid approach.
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