Decode a JWT with a browser-based decoder that parses the token on your own device, so the token and its claims are never sent to a server. It shows the header and payload instantly and is safe to use with real tokens because nothing is transmitted or logged.
A JSON Web Token often carries a user id, session information and scopes, and it is effectively a live credential until it expires. Pasting a real token into a website that decodes it server-side hands your credential to that site. A client-side decoder splits and base64-decodes the token in your browser, so the token never leaves your machine.
Decoding shows the header (algorithm and type) and the payload (the claims), which is enough to check expiry, issuer and scopes while debugging. Note that decoding is not the same as verifying the signature, which requires the secret or public key.
No. The token is decoded entirely in your browser and is never transmitted or stored.
Decoding reveals the header and payload; verifying the signature separately requires the signing key.
Yes. Decoding works regardless of expiry, which is useful for debugging.