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Quickstart for Sellers

This guide walks you through integrating with x402 to enable payments for your API or service. By the end, your API will be able to charge buyers and AI agents for access.

Note: This quickstart begins with testnet configuration for safe testing. When you're ready for production, see Running on Mainnet for the simple changes needed to accept real payments on Base (EVM) and Solana networks.

Prerequisites

Before you begin, ensure you have:

A crypto wallet to receive funds (any EVM-compatible wallet)
Node.js and npm, Go, or Python and pip installed
An existing API or server

Note: The Python SDK is currently under development for x402 v2. For immediate v2 support, use TypeScript or Go.

Note We have pre-configured examples available in our repo for both Node.js and Go. We also have an advanced example that shows how to use the x402 SDKs to build a more complex payment flow.

1. Install Dependencies

Install the x402 Express middleware package.

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

2. Add Payment Middleware

Integrate the payment middleware into your application. You will need to provide:

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.

Full example in the repo here.

Route Configuration Interface:

When a request is made to these routes without payment, your server will respond with the HTTP 402 Payment Required code and payment instructions.

3. Test Your Integration

To verify:

Make a request to your endpoint (e.g., curl http://localhost:4021/weather).
The server responds with a 402 Payment Required, including payment instructions in the PAYMENT-REQUIRED header.
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.
Retry the request, this time including the PAYMENT-SIGNATURE header containing the cryptographic proof of payment.
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)

When using the CDP facilitator, your endpoints can be listed in the x402 Bazaar, our discovery layer that helps buyers and AI agents find services. To enable discovery:

Learn more about the discovery layer in the Bazaar documentation.

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

Once you've tested your integration on testnet, you're ready to accept real payments on mainnet.

1. Update the Facilitator URL

For mainnet, use the CDP facilitator:

2. Update Your Network Identifier

Change from testnet to mainnet network identifiers:

3. Register Multiple Schemes (Multi-Network)

For multi-network support, register both EVM and SVM schemes:

4. Update Your Wallet

Make sure your receiving wallet address is a real mainnet address where you want to receive USDC payments.

5. Test with Real Payments

Before going live:

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

Warning: Mainnet transactions involve real money. Always test thoroughly on testnet first and start with small amounts on mainnet.

Network Identifiers (CAIP-2)

x402 v2 uses CAIP-2 format for network identifiers:

Network

CAIP-2 Identifier

Base Mainnet

eip155:8453

Base Sepolia

eip155:84532

Solana Mainnet

solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp

Solana Devnet

solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1

See Network Support for the full list.

Next Steps

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

For questions or support, join our Discord.

Summary

This quickstart covered:

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

Your API is now ready to accept crypto payments through x402.

PreviousQuickstart for Buyers NextHTTP 402

Last updated 29 days ago

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

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 } from "@x402/next";
import { x402ResourceServer, HTTPFacilitatorClient } from "@x402/core/server";
import { registerExactEvmScheme } from "@x402/evm/exact/server";

const payTo = "0xYourAddress";

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

const server = new x402ResourceServer(facilitatorClient);
registerExactEvmScheme(server);

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 } from "@x402/hono";
import { x402ResourceServer, HTTPFacilitatorClient } from "@x402/core/server";
import { registerExactEvmScheme } from "@x402/evm/exact/server";

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

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

const server = new x402ResourceServer(facilitatorClient);
registerExactEvmScheme(server);

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": {
                Accepts: x402http.PaymentOptions{
                    {
                        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()},
        },
        SyncFacilitatorOnStart: 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")
}

from typing import Any, Dict
from fastapi import FastAPI
from x402.fastapi.middleware import require_payment

app = FastAPI()

# Apply payment middleware to specific routes
app.middleware("http")(
    require_payment(
        path="/weather",
        price="$0.001",
        pay_to_address="0xYourAddress",
        network="base-sepolia",  # v1 string identifier
    )
)

@app.get("/weather")
async def get_weather() -> Dict[str, Any]:
    return {
        "report": {
            "weather": "sunny",
            "temperature": 70,
        }
    }

from flask import Flask
from x402.flask.middleware import PaymentMiddleware

app = Flask(__name__)

# Initialize payment middleware
payment_middleware = PaymentMiddleware(app)

# Apply payment middleware to specific routes
payment_middleware.add(
    path="/weather",
    price="$0.001",
    pay_to_address="0xYourAddress",
    network="base-sepolia",  # v1 string identifier
)

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)
}

{
  "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"],
      },
    },
  },
}

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

import { registerExactEvmScheme } from "@x402/evm/exact/server";
import { registerExactSvmScheme } from "@x402/svm/exact/server";

const server = new x402ResourceServer(facilitatorClient);
registerExactEvmScheme(server);
registerExactSvmScheme(server);

import (
    evm "github.com/coinbase/x402/go/mechanisms/evm/exact/server"
    svm "github.com/coinbase/x402/go/mechanisms/svm/exact/server"
)

r.Use(ginmw.X402Payment(ginmw.Config{
    // ...
    Schemes: []ginmw.SchemeConfig{
        {Network: x402.Network("eip155:8453"), Server: evm.NewExactEvmScheme()},
        {Network: x402.Network("solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp"), Server: svm.NewExactSvmScheme()},
    },
}))