Free JWT Decoder
Decode and inspect JSON Web Tokens. View header, payload, claims, and expiration time. All processing happens in your browser.
Paste a JWT to decode
Your token will be decoded entirely in your browser. No data is sent to any server.
How to Use the JWT Decoder
Paste Your JWT Token
Copy your JWT token and paste it into the input field. The token should be in the standard format: header.payload.signature with three Base64-encoded parts separated by dots.
View Decoded Header
The header section is automatically decoded showing the token type (typ) and signing algorithm (alg) such as HS256, RS256, or ES256 used to create the signature.
Inspect the Payload Claims
Review the payload containing all claims: standard claims like iss, sub, exp, iat, and any custom claims. Timestamps are converted to human-readable dates for easy verification.
Check Token Expiration
The tool automatically checks if the token has expired by comparing the exp claim with the current time. Expired tokens are clearly marked with a warning indicator.
Pro tip: Your data is processed entirely in your browser. Nothing is sent to any server, ensuring complete privacy.
Understanding JSON Web Tokens
JSON Web Tokens (JWTs) are an open standard (RFC 7519) for securely transmitting information between parties as a JSON object. They are commonly used for authentication - after a user logs in, each subsequent request includes the JWT, allowing access to routes, services, and resources permitted with that token.
JWT Structure
- Header: Contains the token type (JWT) and signing algorithm (e.g., HS256, RS256)
- Payload: Contains claims - statements about the user and additional metadata
- Signature: Used to verify the token was not altered and, with asymmetric algorithms, verify the sender
Common Use Cases
- Authentication: Single Sign-On (SSO) and API authentication
- Authorization: Role-based access control using custom claims
- Information Exchange: Securely transmitting data between services
Frequently Asked Questions
What is a JWT (JSON Web Token)?
A JWT is a compact, URL-safe token format used for securely transmitting information between parties. It consists of three parts: a header (algorithm and token type), a payload (claims/data), and a signature. JWTs are commonly used for authentication and information exchange in web applications.
Is it safe to decode JWTs online?
Our JWT decoder processes tokens entirely in your browser - no data is sent to any server. However, JWTs contain sensitive information, so avoid pasting production tokens with real user data into any online tool. For production debugging, use local tools or decode only development/test tokens.
What are JWT claims?
Claims are statements about the user or token. Standard claims include: iss (issuer), sub (subject), aud (audience), exp (expiration), nbf (not before), iat (issued at), and jti (JWT ID). Custom claims can contain any application-specific data like user roles or permissions.
What does the JWT signature do?
The signature ensures the token has not been tampered with. It is created by encoding the header and payload, then signing with a secret (HMAC) or private key (RSA/ECDSA). Verification requires the corresponding secret or public key. This decoder does not verify signatures.
What JWT algorithms are commonly used?
Common algorithms include: HS256 (HMAC with SHA-256) for symmetric signing, RS256 (RSA with SHA-256) for asymmetric signing, and ES256 (ECDSA with SHA-256) for elliptic curve signing. HS256 is simplest, while RS256/ES256 allow public key verification without exposing the signing key.
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