What JWT Decoder does
Decode a JSON Web Token, inspect its claims, and verify HMAC signatures without the token leaving your device.
Also searched as jwt, json web token, decode jwt, token decoder, bearer token, claims, verify jwt, jwt.io.
Split and base64url-decode the segments
Check exp and nbf against your clock
Verify HS256/384/512 when you supply the secret
Offline by construction
No JWKS is fetched, which is why RS and ES tokens report as unverifiable rather than silently passing. Decoding and claim checks still work for every algorithm.
Pasting a token elsewhere leaks it
A JWT is a bearer credential. Decoding it on a hosted site hands that site your session; this one never sends it anywhere.
JWT Decoder FAQ
Does jsontools.me upload my JSON?
No. The document is parsed and processed by json-buf inside a dedicated WebAssembly worker on your device.
Does it work offline?
Yes. After the application shell and engine have loaded once, the installable PWA keeps the tools available without a network connection.