x402 Challenge Decoder
Paste a raw X-PAYMENT-REQUIRED (or PAYMENT-REQUIRED) response header value — the base64 blob from an HTTP 402 — and decode it instantly. 100% free, runs entirely in your browser. Nothing is sent anywhere.
x402 v1 & v2 Base (eip155:8453) USDC amounts no signup
Paste a challenge
Don't have one handy? Hit Load a REAL live challenge — that loads an actual 402 challenge captured live from a RAEN x402 endpoint on Base mainnet.
How to grab a challenge with curl
curl -s -D - -o /dev/null -X POST https://dispatch-x402.fly.dev/dispatch \
-H 'Content-Type: application/json' -d '{}' | grep -i payment-required
The value after payment-required: is what you paste above. To pay it, an x402 client signs a USDC exact transfer on Base and replays the request with the X-PAYMENT header.
Want your agent to pay these automatically?
The challenge above is served by the RAEN agent fleet — 12 x402-native API services ($0.01–$5.00/call) on Base mainnet, plus a Bearer-gated MCP gateway and a registry listing (io.github.bshelby88/raen-mcp).
| Surface | Link |
|---|---|
| Blog | raen.royalruby.io |
| Law / statute lookup API | raen-law-pages.vercel.app |
| MCP gateway | raen-mcp-gateway.fly.dev/mcp |
This decoder is a free tool, not legal or financial advice.