JWT Decoder
Read a JWT header and payload. The signature isn't checked — this is a decoder, not a verifier.
This only reads the header and payload. It does not check the signature.
Header
{
"alg": "none"
}
Payload
{
"sub": "demo"
}Calculations happen in your browser.
Worked example
The sample token decodes to a header of {"alg":"none"} and a payload of {"sub":"demo"}. The third part, the signature, is shown only as text. It isn’t checked.
FAQ
- Does this verify the token?
- No. It only Base64-decodes the header and payload. A valid-looking payload can still be forged.
- What are the three parts?
- Header, payload, and signature, separated by dots. The first two are JSON. The signature is binary and isn’t decoded as JSON.
- Why did decoding fail?
- The header and payload must be Base64url JSON. A token with fewer than two segments, or with damaged padding, will not parse.