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Getting started with Express

Start accepting x402 payments in your Express server in 2 minutes.
You can find the full code for this example here.

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Step 1: Create a new server from the starter template

Use your favorite package manager.
npm (npx)
npx @payai/x402-express-starter my-first-server
pnpm
pnpm dlx @payai/x402-express-starter my-first-server
bun
bunx @payai/x402-express-starter my-first-server
The starter mirrors the upstream example and bootstraps a ready-to-run Express server.

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Step 2: Set your environment variables

Open your generated project’s .env and set:
  • FACILITATOR_URL: Facilitator base URL (defaults to: https://facilitator.payai.network)
  • NETWORK: Network to use for the facilitator (default: base-sepolia)
  • ADDRESS: Wallet public address to receive payments to
FACILITATOR_URL=https://facilitator.payai.network
NETWORK=base-sepolia # or base
ADDRESS=0x... # wallet public address you want to receive payments to

# required if using the Base mainnet facilitator
CDP_API_KEY_ID="Coinbase Developer Platform Key"
CDP_API_KEY_SECRET="Coinbase Developer Platform Key Secret"

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Step 3: Preview the server code

This is the index.ts the starter generates. It loads your env, applies the x402 payment middleware, defines example routes, and logs the server URL. 
import { config } from "dotenv";
import express from "express";
import { paymentMiddleware, Resource } from "x402-express";
config();

const facilitatorUrl = process.env.FACILITATOR_URL as Resource;
const payTo = process.env.ADDRESS as `0x${string}`;

if (!facilitatorUrl || !payTo) {
  console.error("Missing required environment variables");
  process.exit(1);
}

const app = express();

app.use(
  paymentMiddleware(
    payTo,
    {
      "GET /weather": {
        // USDC amount in dollars
        price: "$0.001",
        // network: "base" // uncomment for Base mainnet
        network: "base-sepolia",
      },
      "/premium/*": {
        // Define atomic amounts in any EIP-3009 token
        price: {
          amount: "100000",
          asset: {
            address: "0xabc",
            decimals: 18,
            eip712: {
              name: "WETH",
              version: "1",
            },
          },
        },
        // network: "base" // uncomment for Base mainnet
        network: "base-sepolia",
      },
    },
    {
      url: facilitatorUrl,
    },
  ),
);

app.get("/weather", (req, res) => {
  res.send({
    report: {
      weather: "sunny",
      temperature: 70,
    },
  });
});

app.get("/premium/content", (req, res) => {
  res.send({
    content: "This is premium content",
  });
});

app.listen(4021, () => {
  console.log(`Server listening at http://localhost:${4021}`);
});

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Step 4: Run the server

npm run dev
Your server is now accepting 402 payments!

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Step 5: Test the server

You can test payments against your server locally by following the fetch example or the axios example.

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