Question 1

What is a JSON Web Token (JWT)?

Accepted Answer

A compact, URL-safe token format for transmitting claims between parties. Commonly used for authentication — after login, the server issues a JWT that the client sends with subsequent requests.

Question 2

Is it safe to decode a JWT in the browser?

Accepted Answer

Yes, the payload is just Base64-encoded, not encrypted. Anyone with the token can read it. This tool decodes locally — nothing is sent to a server.

Question 3

What are the three parts of a JWT?

Accepted Answer

Header (algorithm and token type), Payload (claims like user ID and expiration), and Signature (verifies the token has not been tampered with). They are separated by dots.

Question 4

Can this tool verify JWT signatures?

Accepted Answer

No, signature verification requires the secret key or public key used to sign the token. This tool only decodes and displays the header and payload.

JWT Decoder

Frequently Asked Questions