Quickstart for Sellers - x402

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
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

Install the x402 Next.js middleware package.

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

Install the x402 Hono middleware package.

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

Add the x402 Go module to your project:

go get github.com/coinbase/x402/go

Install the x402 Python package with FastAPI support:

pip install "x402[fastapi]"

# For Solana support, also add:
pip install "x402[svm]"

Install the x402 Python package with Flask support:

pip install "x402[flask]"

# For Solana support, also add:
pip install "x402[svm]"

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.

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`);
});

Full example in the repo here.

// 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*"],
};

Full example in the repo here.

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 });

Full example in the repo here.

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")
}

Full example in the repo here.

from typing import Any

from fastapi import FastAPI

from x402.http import FacilitatorConfig, HTTPFacilitatorClient, PaymentOption
from x402.http.middleware.fastapi import PaymentMiddlewareASGI
from x402.http.types import RouteConfig
from x402.mechanisms.evm.exact import ExactEvmServerScheme
from x402.server import x402ResourceServer

app = FastAPI()

# Your receiving wallet address
pay_to = "0xYourAddress"

# Create facilitator client (testnet)
facilitator = HTTPFacilitatorClient(
    FacilitatorConfig(url="https://x402.org/facilitator")
)

# Create resource server and register EVM scheme
server = x402ResourceServer(facilitator)
server.register("eip155:84532", ExactEvmServerScheme())

# Define protected routes
routes: dict[str, RouteConfig] = {
    "GET /weather": RouteConfig(
        accepts=[
            PaymentOption(
                scheme="exact",
                pay_to=pay_to,
                price="$0.001",  # USDC amount in dollars
                network="eip155:84532",  # Base Sepolia (CAIP-2 format)
            ),
        ],
        mime_type="application/json",
        description="Get current weather data for any location",
    ),
}

# Add payment middleware
app.add_middleware(PaymentMiddlewareASGI, routes=routes, server=server)


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


if __name__ == "__main__":
    import uvicorn
    uvicorn.run(app, host="0.0.0.0", port=4021)

Full example in the repo here.

from flask import Flask, jsonify

from x402.http import FacilitatorConfig, HTTPFacilitatorClientSync, PaymentOption
from x402.http.middleware.flask import payment_middleware
from x402.http.types import RouteConfig
from x402.mechanisms.evm.exact import ExactEvmServerScheme
from x402.server import x402ResourceServerSync

app = Flask(__name__)

pay_to = "0xYourAddress"

facilitator = HTTPFacilitatorClientSync(
    FacilitatorConfig(url="https://x402.org/facilitator")
)

server = x402ResourceServerSync(facilitator)
server.register("eip155:84532", ExactEvmServerScheme())

routes: dict[str, RouteConfig] = {
    "GET /weather": RouteConfig(
        accepts=[
            PaymentOption(
                scheme="exact",
                pay_to=pay_to,
                price="$0.001",
                network="eip155:84532",
            ),
        ],
        mime_type="application/json",
        description="Get current weather data for any location",
    ),
}

payment_middleware(app, routes=routes, server=server)


@app.route("/weather")
def get_weather():
    return jsonify({
        "report": {
            "weather": "sunny",
            "temperature": 70,
        }
    })


if __name__ == "__main__":
    app.run(host="0.0.0.0", port=4021)

Route Configuration Interface:

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)
}

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

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

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 a production facilitator. See the x402 Ecosystem for available options. Example using one facilitator:

Node.js
Go
Python (FastAPI)
Python (Flask)

const facilitatorClient = new HTTPFacilitatorClient({
  url: "https://api.cdp.coinbase.com/platform/v2/x402"
});

facilitatorClient := x402http.NewHTTPFacilitatorClient(&x402http.FacilitatorConfig{
    URL: "https://api.cdp.coinbase.com/platform/v2/x402",
})

from x402.http import FacilitatorConfig, HTTPFacilitatorClient

facilitator = HTTPFacilitatorClient(
    FacilitatorConfig(url="https://api.cdp.coinbase.com/platform/v2/x402")
)

from x402.http import FacilitatorConfig, HTTPFacilitatorClientSync

facilitator = HTTPFacilitatorClientSync(
    FacilitatorConfig(url="https://api.cdp.coinbase.com/platform/v2/x402")
)

2. Update Your Network Identifier

Change from testnet to mainnet network identifiers:

Base Mainnet
Solana Mainnet
Multi-Network

// Testnet → Mainnet
network: "eip155:8453", // Base mainnet (was eip155:84532)

// Testnet → Mainnet
network: "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp", // Solana mainnet

// For Solana, use a Solana wallet address (base58 format)
payTo: "YourSolanaWalletAddress",

// 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",
  },
}

3. Register Multiple Schemes (Multi-Network)

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

Node.js
Go
Python

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()},
    },
}))

from x402.mechanisms.evm.exact import ExactEvmServerScheme
from x402.mechanisms.svm.exact import ExactSvmServerScheme
from x402.server import x402ResourceServer

server = x402ResourceServer(facilitator)
server.register("eip155:8453", ExactEvmServerScheme())  # Base mainnet
server.register("solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp", ExactSvmServerScheme())  # Solana mainnet

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

Check out the Advanced Example for a more complex payment flow
Explore Advanced Concepts like lifecycle hooks for custom logic before/after verification/settlement
Explore Extensions like Bazaar for service discovery
Get started as a buyer

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.

HTTP 402For decades, HTTP 402 Payment Required has been reserved for future use. x402 unlocks it, and [absolves the internet of its original sin](https://economyofbits.substack.com/p/marc-andreessens-original-sin).

⌘I

Prerequisites
1. Install Dependencies
2. Add Payment Middleware
3. Test Your Integration
4. Enhance Discovery with Metadata (Recommended)
5. Error Handling
Running on Mainnet
1. Update the Facilitator URL
2. Update Your Network Identifier
3. Register Multiple Schemes (Multi-Network)
4. Update Your Wallet
5. Test with Real Payments
Network Identifiers (CAIP-2)
Next Steps
Summary