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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@latest my-server
pnpm
pnpm dlx @payai/x402-express-starter@latest my-server
bun
bunx @payai/x402-express-starter@latest my-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: 
EVM_ADDRESS=0x...   # EVM wallet address to receive payments
SVM_ADDRESS=...    # Solana wallet address to receive payments
The starter uses @payai/facilitator which automatically connects to the PayAI facilitator — no URL configuration needed.

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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, x402ResourceServer } from "@x402/express";
import { ExactEvmScheme } from "@x402/evm/exact/server";
import { ExactSvmScheme } from "@x402/svm/exact/server";
import { HTTPFacilitatorClient } from "@x402/core/server";
import { facilitator } from "@payai/facilitator";

config();

const evmAddress = process.env.EVM_ADDRESS as `0x${string}`;
const svmAddress = process.env.SVM_ADDRESS;
if (!evmAddress || !svmAddress) {
  console.error("Missing required environment variables");
  process.exit(1);
}

const facilitatorClient = new HTTPFacilitatorClient(facilitator);

const app = express();

app.use(
  paymentMiddleware(
    {
      "GET /weather": {
        accepts: [
          {
            scheme: "exact",
            price: "$0.001",
            network: "eip155:84532",
            payTo: evmAddress,
          },
          {
            scheme: "exact",
            price: "$0.001",
            network: "solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1",
            payTo: svmAddress,
          },
        ],
        description: "Weather data",
        mimeType: "application/json",
      },
    },
    new x402ResourceServer(facilitatorClient)
      .register("eip155:84532", new ExactEvmScheme())
      .register("solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1", new ExactSvmScheme()),
  ),
);

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

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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Going to production

The starter works on the free tier out of the box — no API keys required. When you’re ready for production, create a merchant account at merchant.payai.network, get your API keys, and add them to your .env: 
PAYAI_API_KEY_ID=your-key-id
PAYAI_API_KEY_SECRET=your-key-secret
The @payai/facilitator package automatically detects these environment variables and authenticates your requests to the facilitator. See Facilitator Pricing for tier details and Facilitator Authentication for the full protocol reference.

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x402 reference

For a deeper dive into message shapes, headers, verification and settlement responses, see the x402 Reference.

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