Waiting for a valid JWT
Paste a JWT to decode it locally.
JWT Security Checker
Decode and review JWTs for common implementation mistakes: alg none, missing expiration, long-lived access tokens, sensitive data in payloads, insecure storage assumptions, and signature verification gaps.
Local JWT input
No server uploadCheck token security
Paste a JWT to decode it locally.
Explain This Token
Paste a JWT to decode it locally.
Decoded Header
Header will appear here.
Decoded Payload
Payload will appear here.
Claims Timeline
Issued atNot present
Not beforeNot present
Expires atNot present
Expected claims
Local checksClaim Validation Panel
Local verification
idleSignature Verification Option
JWKS verification
idleVerify With JWKS URL
Security Findings
Storage Guidance
JWT payloads are readable by anyone who has the token. Do not put passwords, refresh tokens, private keys, API keys, payment data, or unnecessary personal data inside the payload.
Browser storage choice matters. localStorage and sessionStorage are easy to use but exposed to JavaScript if XSS occurs. For browser apps, prefer short-lived access tokens and consider HttpOnly, Secure, SameSite cookies for server-managed sessions.
Always verify signatures on the server, pin the expected algorithm, validate iss and aud, enforce exp, and rotate signing keys safely.
Safe sharing
No secret copyRedact Token for Tickets or Chat
Best architecture for JWT checking
The safest design is client-side by default. JWTs often contain authentication claims, user identifiers, scopes, and sometimes accidental sensitive data, so this tool decodes and checks them in the browser instead of sending them to a Cyberonz API.
For background reading, see what a JWT token is and common JWT security mistakes.