JWT Decoder | Decode JSON Web Tokens Instantly
Decode and inspect JSON Web Tokens (JWT) instantly in your browser. View header, payload, standard claims (exp, iss, aud, sub, iat, nbf) and timestamps. Runs locally—no upload or verification required.
How to Use This Tool
- 1
Paste your JWT in the input box (header.payload.signature).
- 2
Header, payload, and signature will be decoded instantly.
- 3
View claims like exp, iat, and nbf with auto-converted timestamps.
- 4
Copy decoded data for debugging or documentation.
- 5
Always verify signatures server-side before trusting token contents.
Use Cases & Examples
API Authentication Debugging
Inspect API authentication tokens for claims, expiration, and issuer/audience during debugging.
OAuth 2.0 & OpenID Connect Development
Decode access and ID tokens to check validity, claims, and configuration during OAuth2/OIDC development.
App & Frontend Token Debugging
Debug JWTs used in web or mobile apps to verify token lifetime, storage, and refresh logic.
Security Auditing & Analysis
Analyze algorithms and claims to ensure proper security and no sensitive data in payloads.
How JWT Works
A JWT is composed of three Base64URL-encoded parts: header, payload, and signature.
Header contains the algorithm (alg) and token type (typ). Payload contains claims (exp, iss, aud, sub, iat, nbf).
The signature ensures integrity using HMAC or RSA/ECDSA, not encryption. Tokens are readable once decoded.
Frequently Asked Questions
Q.Does this verify JWT signatures?
A. No. This tool only decodes the JWT and does not verify its signature. Always validate the signature on your server using the correct key.
Q.Are JWTs encrypted? Is decoding safe?
A. JWTs are not encrypted, only Base64URL-encoded. Never include passwords, secrets, or personal data inside a JWT payload.
Q.What are JWT claims and what do they mean?
A. Claims are pieces of data in the token like exp (expiration), iss (issuer), aud (audience), sub (subject), iat (issued at), and nbf (not before). Defined in RFC 7519.
Q.How can I check if a JWT is expired?
A. Check the 'exp' claim, which shows expiration in Unix time. Tokens that are expired should be rejected by the server.
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