x402 header decoder

Paste the value of a PAYMENT-REQUIRED, PAYMENT-SIGNATURE or PAYMENT-RESPONSE header to read what it contains.

Decoding happens in your browser and nothing is sent to this site. That matters for PAYMENT-SIGNATURE values, which anyone holding them can submit for settlement until they expire.

Get a value to try

curl -si https://x402testendpoint.com/t/ok | grep -i '^payment-required'

From a script or agent

GET /api/decode?value=… returns the same decoding as JSON, with notes on price and expiry. It is also the decode_header tool on the MCP server. Do not send a live payment signature to any third-party service, this one included.

See the 402 response format for what each field means.