Quick Start

Server Setup

Install the x402 middleware for your framework and point it at the OpenX402 facilitator. No sign up required.

With Express

npm install express x402-express

import express from "express";
import { paymentMiddleware } from "x402-express";

const app = express();

app.use(
  paymentMiddleware(
    "0xYourWalletAddress" as `0x${string}`,
    {
      "/api/premium": {
        price: "$0.10",
        network: "base",
        config: { description: "Premium API access" },
      },
    },
    {
      url: "https://facilitator.openx402.ai",
    }
  )
);

app.get("/api/premium", (req, res) => {
  res.json({ data: "premium content", payer: req.payer });
});

app.listen(3000);

With Hono

npm install hono x402-hono

import { Hono } from "hono";
import { paymentMiddleware } from "x402-hono";

const app = new Hono();

app.use(
  "/api/*",
  paymentMiddleware(
    "0xYourWalletAddress" as `0x${string}`,
    {
      "/api/premium": {
        price: "$0.10",
        network: "base",
        config: { description: "Premium API access" },
      },
    },
    {
      url: "https://facilitator.openx402.ai",
    }
  )
);

app.get("/api/premium", (c) => {
  return c.json({ data: "premium content" });
});

export default app;

Client Setup

Use x402-fetch to make payments automatically from the client side:

import { wrapFetch } from "x402-fetch";

const x402Fetch = wrapFetch(fetch, {
  privateKey: process.env.PRIVATE_KEY as `0x${string}`,
});

const response = await x402Fetch("https://your-server.com/api/premium");
const data = await response.json();

When the server returns 402 Payment Required, x402-fetch automatically:

Reads the payment requirements from the response
Signs a transferWithAuthorization with the client's private key
Resends the request with the signed payment headers

The client never sends a transaction — it only signs an authorization that the facilitator executes on-chain.

Solana Client

import { wrapFetch } from "x402-fetch";
import { svm } from "x402/shared";

const signer = await svm.createSignerFromBase58(process.env.SOLANA_PRIVATE_KEY);
const x402Fetch = wrapFetch(fetch, signer);

const response = await x402Fetch("https://your-server.com/api/premium");
const data = await response.json();

Test on Base Sepolia

Use network: "base-sepolia" during development. Get testnet USDC from the Circle faucet.

Next Steps

Building a Server — dynamic pricing, per-route config, and more patterns
Facilitator API — what happens under the hood when verify and settle are called
Supported Chains — networks and contract addresses