JWT Decoder & Token Inspector

How to Decode and Inspect JSON Web Tokens (JWT)

1. Paste Your Encoded Token: Paste your JWT into the input field above, or test with a preloaded sample token.
2. Inspect the Color-Coded Segments: A standard JWT is split into three parts: Header (rose), Payload (purple), and Signature (cyan).
3. Verify Expiration Dates: The tool automatically converts Unix epoch timestamps into human-readable local dates and relative times (e.g. “Expires in 2 hours” or “Expired 4 days ago”). To calculate custom timestamps or compare global timezones, use our Unix and epoch timestamp converter.
4. Review Claims: Inspect user identifiers (sub), authorized roles, audience parameters (aud), and custom token claims.
5. One-Click Copy: Copy decoded JSON claims directly into your editor or API client.

Understanding the Three Components of a JWT

• 1. Header: Contains cryptographic metadata, primarily the signature algorithm used (e.g. HS256 or RS256) and the token type (JWT).
• 2. Payload: Contains the claims - statements about the user and entity alongside metadata like issuance time (iat) and expiration (exp).
• 3. Signature: A cryptographic hash generated by combining the encoded header and payload with a secret key, ensuring the token was not tampered with in transit.

Critical JWT Security Best Practices

• JWTs Are Encoded, Not Encrypted: Anyone who intercepts a JWT can decode the Base64URL payload. Never store database passwords, API secrets, or credit card numbers in claims.
• Always Check Expiration on the Backend: Never rely exclusively on client-side expiration checks; API gateways must reject requests whose exp timestamp has passed.
• 100% Client-Side Inspection: Decoding occurs exclusively in your browser's JavaScript engine, ensuring production auth tokens are never stored or logged on an external server.