Free browser tool - Updated 2026-07-06
Payment Header Decoder
Paste a Base64 x402 header value and inspect the decoded JSON, detected version, likely header type, and field-by-field meaning without sending the payload anywhere.
Decoded result
Detected version
-
Likely type
-
JSON
| Field | Value | Meaning |
|---|
Decoder limits
This tool only decodes Base64 JSON and explains common x402 fields. It does not contact a facilitator, read chain state, verify signatures, validate balances, or prove that settlement happened.
For production support, pair decoded fields with the original route requirements, request fingerprint, facilitator response, and settlement logs. That is the evidence needed to distinguish bad header shape from bad payment authorization.
How to use it
- Paste the Base64 header value, with or without the header name prefix.
- Review the detected x402 version and likely header type.
- Inspect the decoded JSON and field explanations.
- Use the migration hints when the object looks like a legacy v1 header.
FAQ
Can this verify a signature?
No. It decodes and explains the JSON wrapper. Cryptographic verification still requires the selected scheme, network rules, payment requirements, and often facilitator or chain access.
Does it support v1 headers?
It detects common v1 markers and legacy header names, but the field explanations focus on the modern v2 shape because new integrations should migrate to PAYMENT-SIGNATURE and PAYMENT-RESPONSE.
Is it safe to paste production headers?
The tool is client-side only, but payment headers can expose resource URLs, wallet addresses, and signed authorization metadata. Treat production payloads as sensitive support artifacts.