Header
Payload
Signature
..
Decode and inspect JSON Web Tokens
Algorithm: -
The signature is used to verify the sender's identity and ensure the message hasn't been altered.
Note: This tool only decodes tokens. To verify the signature, you need the secret key or public key.
JSON Web Token (JWT) is an open standard (RFC 7519) for securely transmitting information between parties as a JSON object. JWTs are commonly used for authentication and authorization in web applications.
A JWT consists of three parts separated by dots:
• Header - Contains token type and signing algorithm
• Payload - Contains claims (user data and metadata)
• Signature - Verifies token integrity
iss - Issuer of the token
sub - Subject (usually user ID)
aud - Audience (intended recipient)
exp - Expiration time
nbf - Not before time
iat - Issued at time
jti - JWT ID (unique identifier)
A JWT decoder helps you inspect token headers and payload claims quickly when authentication issues are blocking a login or API call.
JWT Decoder helps when you need Parse JWT tokens in one tab instead of switching to desktop software or a temporary script.
header.alg: HS256\npayload.sub: user_123\npayload.exp: 1700000000No. Decoding reveals readable claims, but signature verification still requires the correct signing context.
exp, iat, iss, aud, and sub usually explain most login and authorization failures.
It speeds up debugging when you need a quick look at claims without opening a REPL or writing a script.