x402.fairseal.io

Create a tamper-proof on-chain record of any content hash. Submit a SHA-256 hash; returns a cryptographic proof of existence anchored to Base mainnet via Merkle batch. Poll status_url for verifiable receipt with on-chain tx hash. $0.02 USDC per anchor. Audit trail for AI decisions or documents.

Open endpoint ↗

Price per call: $0.02
Chain: Base
Method: POST
Paid calls · 30 days: 9

Call it from code

This API is run by its own provider and paid directly through x402. We list it so you can find it; we don't route or hold the payment.

import { x402Client, wrapFetchWithPayment } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";

const client = new x402Client();
registerExactEvmScheme(client, { signer: agentAccount });

const pay = wrapFetchWithPayment(fetch, client);
const res = await pay("https://x402.fairseal.io/v2/anchor", { method: "POST" });
console.log(await res.json());

https://x402.fairseal.io/v2/anchor