Question 1

What is a JWT token?

Accepted Answer

A JSON Web Token securely carries data between parties. It has three Base64URL-encoded parts separated by dots: a header, a payload and a signature.

Question 2

Does the JWT decoder send my token to a server?

Accepted Answer

No. Decoding happens entirely in your browser, so the token never leaves your device and you can safely inspect its contents.

Question 3

Does decoding a JWT verify the signature?

Accepted Answer

Decoding only reads the header and payload. It does not confirm the signature. Verification requires the key the token was signed with.

Tools
JWT decoder

JWT decoder