JWT Decoder & Debugger
Inspect JWT headers and claims, and sign or verify HMAC JWTs using HS256, HS384 or HS512. Decoding a payload does not establish that the token is trusted.
Real-time Results
Header (Decoded)
Specifies metadata details about the token.
{
"alg": "HS256",
"typ": "JWT"
}Payload (Decoded Claims)
Token claims including subject, issuer, and expiration date.
{
"sub": "1234567890",
"name": "John Doe",
"iat": 1516239022
}Security Audit Report
Real-time verification of token expiry and signature validity.
=== CRYPTOGRAPHIC HEALTH REPORT === [SIGNATURE CHECK] ✗ Invalid Signature (Signature Mismatch / Key Incorrect) [EXPIRATION STATUS] : UNKNOWN [DETAILS] : No exp (expiration time) claim detected in token. Algorithm: HS256 | Target: HS-HMAC-Family Privacy Note: Calculated 100% offline. No secrets left your device.
Why Choose JWT Decoder & Debugger
Inspect JWT headers and claims, and sign or verify HMAC JWTs using HS256, HS384 or HS512. Decoding a payload does not establish that the token is trusted.
How to Calculate
- 1Choose Decode to inspect an existing three-part token, or Encode to enter a header and payload.
- 2For HMAC verification or signing, select the supported algorithm and enter the matching secret.
- 3Check the signature status and time claims separately; do not treat decoded claims as authorization.
Frequently Asked Questions (FAQ)
Does decoding prove a token is valid?
No. A JWT payload is readable without its secret. Signature verification requires the correct key and algorithm, and an application must also validate issuer, audience and relevant time claims.
Can this tool verify RS256 or ES256?
No. The implemented signing choices are HS256, HS384 and HS512. RSA and elliptic-curve signatures require a different verifier.
Does a verified signature mean a token is unexpired?
No. Signature integrity and claim validation are separate. A token can have a matching signature and still be expired or intended for a different audience.
Authoritative References & Sources
RFC 7519 — JWT
View SourceRelated Calculators
More calculators selected by category and topic.