JWT Decoder Online

What is a JWT Decoder and Why Do You Need It?

JSON Web Tokens (JWT) are the backbone of modern web authentication. They are used to securely transmit information between parties as a JSON object. However, because they are Base64Url encoded, they look like a string of random characters to the human eye. Our JWT Decoder Online allows you to "unmask" these tokens instantly.

Whether you're debugging an OAuth2 flow, checking session expiration times, or verifying user roles (claims), being able to read the payload is essential. Unlike other tools, our decoder is built with privacy in mind—all processing happens on your device. If you're working with other encoded formats, you might also find our Base64 Encoder/Decoder useful for manual data handling.

Key Features of Our JWT Viewer

• Instant Parsing: Just paste your token, and the header and payload appear immediately.
• No Secret Key Required: Since JWTs are encoded, not encrypted, you can view the data without the private signature key.
• Security First: Your tokens never leave your browser. We don't log or store any data you paste.
• Formatted JSON: The output is automatically beautified, much like our JSON Formatter, making it easy to read nested objects.
• Mobile Friendly: Debug on the go with a fully responsive interface.

How to Use the JWT Decoder

1. Copy your token: Grab the JWT from your application's network tab or local storage.
2. Paste: Drop the string into the "Encoded Token" input field above.
3. Inspect: Look at the Header (red) for the algorithm and the Payload (blue) for user data and timestamps.
4. Copy Results: Use the copy button to quickly grab the JSON data for your documentation or bug reports.

Understanding JWT Structure

A standard JWT consists of three parts separated by dots: Header.Payload.Signature. The header typically contains the type of token and the hashing algorithm used (like HS256 or RS256). The payload contains the "claims," which are statements about an entity (typically, the user) and additional data. Finally, the signature is used to verify that the sender of the JWT is who it says it is and to ensure that the message wasn't changed along the way.

If you are building secure systems, you might also want to use our Password Generator to create strong secrets for your JWT signing keys.