Unpack Your Tokens with the JWT Decoder
Are you working with modern web authentication and staring at a long, seemingly random string of characters? JSON Web Tokens are everywhere, but they aren’t human-readable by default. Instantly inspect the claims and payload of your tokens with our developer-focused JWT Decoder.
What is the JWT Decoder?
The JWT Decoder is an essential debugging tool for developers working with authentication and authorization. A JWT (JSON Web Token) consists of three base64-url encoded parts: the Header, the Payload (claims), and the Signature. This tool instantly decodes the Header and Payload, displaying the JSON data clearly so you can verify user IDs, expiration times, and permissions stored within the token.
Step-by-Step Guide: How to Use It
- Paste Your Token: Copy the complete JWT string (usually starting with
eyJ) and paste it into the “Encoded Token” input area. - Instant Decoding: The tool automatically decodes the token in real-time as you paste it.
- Inspect the Data: Review the output sections. You will see the structured JSON for the Header (algorithm and token type) and the Payload (data claims).
- Signature Verification (Optional): If you provide the secret key, the tool can also verify if the token’s signature is valid.
Practical Use Cases
- Debugging Logins: Verify that your authentication server is correctly embedding the required user roles and IDs inside the token payload upon login.
- Checking Expiration: Quickly decode a token to check the
exp(expiration time) claim to troubleshoot issues with sessions timing out unexpectedly. - API Development: Ensure that the API requests your frontend is sending contain correctly formatted tokens before they hit the backend middleware.
Frequently Asked Questions
- Can a JWT be decrypted? JWTs are usually only encoded (Base64), not encrypted. This means anyone with a decoder can read the payload. You should never put sensitive data like passwords inside a standard JWT.
- What happens if I change the payload? If you modify the payload, the token’s signature will become invalid. A secure server will reject any token where the signature does not match the payload.
- Is my token secure here? Yes, our tool decodes the token entirely within your browser using JavaScript. The token is never sent to a backend server.