JWT Decoder
What is a JWT Decoder?
Decode JSON Web Tokens (JWT) instantly into readable JSON objects: Header (algorithm & token type), Payload claims (user ID, roles, exp, iat), and Signature verification info.
Why Use This Tool?
- API Authentication Debugging: Inspect JWT payload claims, user roles, and token expiration timestamps.
- Token Troubleshooting: Check if a token has expired (`exp`) or contains missing permission claims.
- Security Verification: Inspect token header algorithm (`HS256`, `RS256`).
How to Use
- Paste your encoded JWT string (`ey...`).
- View decoded JSON Header, Payload, and Signature sections side-by-side.
- Check automatic expiration status indicator.
Real Working Example
Input:
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkFsaWNlIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c
Output Result:
Header: { "alg": "HS256", "typ": "JWT" }
Payload: { "sub": "1234567890", "name": "Alice", "iat": 1516239022 }
Important Technical Details & Features
- Base64URL Decoding: Decodes standard Base64URL header and payload parts cleanly.
- Expiration Time Analysis: Converts `exp` and `iat` numeric timestamps into human dates.
- 100% Local Browser Safety: Tokens are never transmitted to any server—your auth secrets remain private.
Related Web & SEO Tools
- JWT Generator: Generate JSON Web Tokens.
- Base64 Converter: Decode Base64 strings.
- Unix Timestamp Converter: Convert epoch timestamps.
Frequently Asked Questions
Does decoding a JWT token verify its cryptographic signature?
Decoding inspects Header and Payload claims; full signature verification requires your secret or public key.
How does it display token expiration (exp) and issued-at (iat) timestamps?
Numeric epoch timestamps are automatically converted into human-readable local dates.
Is my secret JWT authentication token uploaded to any server?
No, JWT token parsing happens 100% locally inside your browser memory.
What algorithms are indicated in the JWT Header?
Displays signing algorithm strings such as HS256, RS256, or ES256.
Can I inspect custom user role claims inside the payload?
Yes, all decoded payload claim key-value pairs are displayed as formatted JSON.