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1. Try the sandbox

The sandbox facilitator is free, requires no API key, and runs on Base Sepolia and Solana Devnet (testnets). 
https://x402.renvoy.ai/sandbox
You can point any x402-compatible server at this URL immediately.

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2. Add payments to your server

Install the Express middleware: 
npm install @x402/express @x402/evm @x402/core
Create a server with a paid endpoint: 
import express from "express";
import { paymentMiddleware, x402ResourceServer } from "@x402/express";
import { ExactEvmScheme } from "@x402/evm/exact/server";
import { HTTPFacilitatorClient } from "@x402/core/server";

const app = express();
const facilitatorClient = new HTTPFacilitatorClient({
  url: "https://x402.renvoy.ai/sandbox",
});

app.use(
  paymentMiddleware(
    {
      "GET /weather": {
        accepts: [
          {
            scheme: "exact",
            price: "$0.001",
            network: "eip155:84532",       // Base Sepolia
            payTo: "0xYOUR_WALLET_ADDRESS", // receives USDC
          },
        ],
        description: "Weather data",
        mimeType: "application/json",
      },
    },
    new x402ResourceServer(facilitatorClient)
      .register("eip155:84532", new ExactEvmScheme()),
  ),
);

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

app.listen(4021);
Test it: 
curl -i http://localhost:4021/weather
# Returns 402 Payment Required with payment details

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3. Pay with a client

Install the fetch wrapper: 
npm install @x402/fetch @x402/evm viem

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

const signer = privateKeyToAccount("0xYOUR_PRIVATE_KEY");
const client = new x402Client();
registerExactEvmScheme(client, { signer });

const fetchWithPayment = wrapFetchWithPayment(fetch, client);

const response = await fetchWithPayment("http://localhost:4021/weather");
const data = await response.json();
console.log(data); // { weather: "sunny", temperature: 70 }
The client wallet needs USDC on the target network. Get testnet USDC from the Circle faucet (supports both Base Sepolia and Solana Devnet).

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4. Go to production

When you’re ready for mainnet:
  1. Sign up at renvoy.ai
  2. Get your API key from the dashboard
  3. Swap the facilitator URL:
- url: "https://x402.renvoy.ai/sandbox"
+ url: "https://x402.renvoy.ai/v1/YOUR_API_KEY"
  1. Change the network to mainnet:
- network: "eip155:84532",  // Base Sepolia
+ network: "eip155:8453",   // Base mainnet
Or for Solana: 
- network: "solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1",  // Solana Devnet
+ network: "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",   // Solana mainnet
That’s it. Same code, real payments. See Plans & Pricing to choose a plan, or jump to the Integration Guide for framework-specific details.