📑 JWT Decoder
⚡ Output
ℹ️ About JWT Decoder
The JWT Decoder is a diagnostic utility for inspecting the contents of a JSON Web Token. Because JWTs are Base64URL encoded, they are not human-readable at a glance, but they are not encrypted by default.
This tool splits the token into its three constituent parts—Header, Payload, and Signature—and decodes them into a structured JSON format. This allows you to verify the claims inside the token (like user IDs, expiration timestamps, and scopes) and check which algorithm was used for signing. It is an essential tool for developers debugging authentication flows and security auditors verifying token-based security.
📖 How to use JWT Decoder
- 1. Paste your full JWT string (including the dots) into the input field.
- 2. Click 'Run Tool' to decode the segments.
- 3. Analyze the 'Header' to see the algorithm and 'Payload' to see the user data.
- 4. Note: This tool does not verify the signature; it only decodes the data.
❓ Frequently Asked Questions
Do I need a secret key to decode a JWT?
No. The data in a JWT is only encoded, not encrypted. Anyone can decode it. You only need the secret key to <strong>verify</strong> if the token is authentic and hasn't been modified.
What is the 'exp' field in the payload?
The <code>exp</code> (Expiration) field is a Unix timestamp indicating when the token becomes invalid. Most systems will reject a token if the current time is greater than this value.
Why does my token say 'Invalid format'?
A valid JWT must have three parts separated by dots (header.payload.signature). Ensure you haven't missed any characters when copying.
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