Quickstart for Sellers

​

Prerequisites

• A crypto wallet to receive funds (any EVM-compatible wallet, e.g., CDP Wallet)
• (Optional) A Coinbase Developer Platform (CDP) account and API Keys
  • Required for mainnet use until other facilitators go live
• Node.js and npm, or Go installed
• An existing API or server

​

1. Install Dependencies

npm install @x402/express @x402/evm @x402/core

npm install @x402/next @x402/evm @x402/core

npm install @x402/hono @x402/evm @x402/core

go get github.com/coinbase/x402/go

​

2. Add Payment Middleware

• The Facilitator URL or facilitator client. For testing, use https://x402.org/facilitator which works on Base Sepolia and Solana Devnet.
  • For mainnet setup, see Running on Mainnet
• The routes you want to protect
• Your receiving wallet address

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();

// Your receiving wallet address
const payTo = "0xYourAddress";

// Create facilitator client (testnet)
const facilitatorClient = new HTTPFacilitatorClient({
  url: "https://x402.org/facilitator"
});

// Create resource server and register EVM scheme
const server = new x402ResourceServer(facilitatorClient)
  .register("eip155:84532", new ExactEvmScheme());

app.use(
  paymentMiddleware(
    {
      "GET /weather": {
        accepts: [
          {
            scheme: "exact",
            price: "$0.001", // USDC amount in dollars
            network: "eip155:84532", // Base Sepolia (CAIP-2 format)
            payTo,
          },
        ],
        description: "Get current weather data for any location",
        mimeType: "application/json",
      },
    },
    server,
  ),
);

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

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

// middleware.ts
import { paymentProxy, x402ResourceServer } from "@x402/next";
import { ExactEvmScheme } from "@x402/evm/exact/server";
import { HTTPFacilitatorClient } from "@x402/core/server";

const payTo = "0xYourAddress";

const facilitatorClient = new HTTPFacilitatorClient({
  url: "https://x402.org/facilitator"
});

const server = new x402ResourceServer(facilitatorClient)
  .register("eip155:84532", new ExactEvmScheme());

export const middleware = paymentProxy(
  {
    "/api/protected": {
      accepts: [
        {
          scheme: "exact",
          price: "$0.01",
          network: "eip155:84532",
          payTo,
        },
      ],
      description: "Access to protected content",
      mimeType: "application/json",
    },
  },
  server,
);

export const config = {
  matcher: ["/api/protected/:path*"],
};

import { Hono } from "hono";
import { serve } from "@hono/node-server";
import { paymentMiddleware, x402ResourceServer } from "@x402/hono";
import { ExactEvmScheme } from "@x402/evm/exact/server";
import { HTTPFacilitatorClient } from "@x402/core/server";

const app = new Hono();
const payTo = "0xYourAddress";

const facilitatorClient = new HTTPFacilitatorClient({
  url: "https://x402.org/facilitator"
});

const server = new x402ResourceServer(facilitatorClient)
  .register("eip155:84532", new ExactEvmScheme());

app.use(
  paymentMiddleware(
    {
      "/protected-route": {
        accepts: [
          {
            scheme: "exact",
            price: "$0.10",
            network: "eip155:84532",
            payTo,
          },
        ],
        description: "Access to premium content",
        mimeType: "application/json",
      },
    },
    server,
  ),
);

app.get("/protected-route", (c) => {
  return c.json({ message: "This content is behind a paywall" });
});

serve({ fetch: app.fetch, port: 3000 });

package main

import (
    "net/http"
    "time"

    x402 "github.com/coinbase/x402/go"
    x402http "github.com/coinbase/x402/go/http"
    ginmw "github.com/coinbase/x402/go/http/gin"
    evm "github.com/coinbase/x402/go/mechanisms/evm/exact/server"
    "github.com/gin-gonic/gin"
)

func main() {
    payTo := "0xYourAddress"
    network := x402.Network("eip155:84532") // Base Sepolia (CAIP-2 format)

    r := gin.Default()

    // Create facilitator client
    facilitatorClient := x402http.NewHTTPFacilitatorClient(&x402http.FacilitatorConfig{
        URL: "https://x402.org/facilitator",
    })

    // Apply x402 payment middleware
    r.Use(ginmw.X402Payment(ginmw.Config{
        Routes: x402http.RoutesConfig{
            "GET /weather": {
                Scheme:      "exact",
                PayTo:       payTo,
                Price:       "$0.001",
                Network:     network,
                Description: "Get weather data for a city",
                MimeType:    "application/json",
            },
        },
        Facilitator: facilitatorClient,
        Schemes: []ginmw.SchemeConfig{
            {Network: network, Server: evm.NewExactEvmScheme()},
        },
        Initialize: true,
        Timeout:    30 * time.Second,
    }))

    // Protected endpoint
    r.GET("/weather", func(c *gin.Context) {
        c.JSON(http.StatusOK, gin.H{
            "weather":     "sunny",
            "temperature": 70,
        })
    })

    r.Run(":4021")
}

interface RouteConfig {
  accepts: Array<{
    scheme: string;           // Payment scheme (e.g., "exact")
    price: string;            // Price in dollars (e.g., "$0.01")
    network: string;          // Network in CAIP-2 format (e.g., "eip155:84532")
    payTo: string;            // Your wallet address
  }>;
  description?: string;       // Description of the resource
  mimeType?: string;          // MIME type of the response
  extensions?: object;        // Optional extensions (e.g., Bazaar)
}

​

3. Test Your Integration

1. Make a request to your endpoint (e.g., curl http://localhost:4021/weather).
2. The server responds with a 402 Payment Required, including payment instructions in the PAYMENT-REQUIRED header.
3. Complete the payment using a compatible client, wallet, or automated agent. This typically involves signing a payment payload, which is handled by the client SDK detailed in the Quickstart for Buyers.
4. Retry the request, this time including the PAYMENT-SIGNATURE header containing the cryptographic proof of payment.
5. The server verifies the payment via the facilitator and, if valid, returns your actual API response (e.g., { "data": "Your paid API response." }).

​

4. Enhance Discovery with Metadata (Recommended)

{
  "GET /weather": {
    accepts: [
      {
        scheme: "exact",
        price: "$0.001",
        network: "eip155:8453",
        payTo: "0xYourAddress",
      },
    ],
    description: "Get real-time weather data including temperature, conditions, and humidity",
    mimeType: "application/json",
    extensions: {
      bazaar: {
        discoverable: true,
        category: "weather",
        tags: ["forecast", "real-time"],
      },
    },
  },
}

​

5. Error Handling

• If you run into trouble, check out the examples in the repo for more context and full code.
• Run npm install or go mod tidy to install dependencies

​

Running on Mainnet

​

Setting Up CDP Facilitator for Production

​

1. Set up CDP API Keys

1. Sign up at cdp.coinbase.com
2. Create a new project
3. Generate API credentials
4. Set the following environment variables:
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   CDP_API_KEY_ID=your-api-key-id
   CDP_API_KEY_SECRET=your-api-key-secret
   

​

2. Update Your Code

import { paymentMiddleware, x402ResourceServer } from "@x402/express";
import { ExactEvmScheme } from "@x402/evm/exact/server";
import { HTTPFacilitatorClient } from "@x402/core/server";

// For mainnet, use CDP's facilitator with API keys
const facilitatorClient = new HTTPFacilitatorClient({
  url: "https://api.cdp.coinbase.com/platform/v2/x402",
  // Add auth headers if required
});

const server = new x402ResourceServer(facilitatorClient)
  .register("eip155:8453", new ExactEvmScheme()); // Base mainnet

app.use(
  paymentMiddleware(
    {
      "GET /weather": {
        accepts: [
          {
            scheme: "exact",
            price: "$0.001",
            network: "eip155:8453", // Base mainnet (CAIP-2)
            payTo: "0xYourAddress",
          },
        ],
        description: "Weather data",
        mimeType: "application/json",
      },
    },
    server,
  ),
);

// Update network to mainnet
network := x402.Network("eip155:8453") // Base mainnet (CAIP-2)

// Create facilitator client for mainnet
facilitatorClient := x402http.NewHTTPFacilitatorClient(&x402http.FacilitatorConfig{
    URL: "https://api.cdp.coinbase.com/platform/v2/x402",
    // Add auth if required
})

r.Use(ginmw.X402Payment(ginmw.Config{
    Routes: x402http.RoutesConfig{
        "GET /weather": {
            Scheme:  "exact",
            PayTo:   payTo,
            Price:   "$0.001",
            Network: network,
        },
    },
    Facilitator: facilitatorClient,
    Schemes: []ginmw.SchemeConfig{
        {Network: network, Server: evm.NewExactEvmScheme()},
    },
}))

​

3. Update Your Wallet

​

4. Test with Real Payments

1. Test with small amounts first
2. Verify payments are arriving in your wallet
3. Monitor the facilitator for any issues

​

Using Different Networks

// Base mainnet
{
  scheme: "exact",
  price: "$0.001",
  network: "eip155:8453", // Base mainnet
  payTo: "0xYourAddress",
}

// Base Sepolia testnet
{
  scheme: "exact",
  price: "$0.001",
  network: "eip155:84532", // Base Sepolia
  payTo: "0xYourAddress",
}

// Solana mainnet
{
  scheme: "exact",
  price: "$0.001",
  network: "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp", // Solana mainnet
  payTo: "YourSolanaWalletAddress",
}

// Solana devnet
{
  scheme: "exact",
  price: "$0.001",
  network: "solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1", // Solana devnet
  payTo: "YourSolanaWalletAddress",
}

// Support multiple networks on the same endpoint
{
  "GET /weather": {
    accepts: [
      {
        scheme: "exact",
        price: "$0.001",
        network: "eip155:8453",
        payTo: "0xYourEvmAddress",
      },
      {
        scheme: "exact",
        price: "$0.001",
        network: "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
        payTo: "YourSolanaAddress",
      },
    ],
    description: "Weather data",
  },
}

​

Network Identifiers (CAIP-2)

​

Next Steps

• Looking for something more advanced? Check out the Advanced Example
• Get started as a buyer
• Learn about the Bazaar discovery layer

​

Summary

• Installing the x402 SDK and relevant middleware
• Adding payment middleware to your API and configuring it
• Testing your integration
• Deploying to mainnet with CAIP-2 network identifiers