Quickstart for Buyers

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Facilitator URLs

Environment	Facilitator URL	Networks	Auth
CDP (recommended)	`https://api.cdp.coinbase.com/platform/v2/x402`	Base, Base Sepolia, Polygon, Arbitrum, World, World Sepolia, Solana, Solana Devnet	CDP API keys required
x402.org (testnet only)	`https://x402.org/facilitator`	Base Sepolia, Solana Devnet	None

We recommend the CDP facilitator for both testnet and mainnet. Use x402.org if you want to try x402 without signing up. This guide walks you through how to use x402 to interact with services that require payment. By the end of this guide, you will be able to programmatically discover payment requirements, complete a payment, and access a paid resource. The x402 helper packages for various languages greatly simplify your integration with x402. You’ll be able to automatically detect payment challenges, authorize payments onchain, and retry requests with minimal code. The packages will automatically trigger the following flow:

Makes the initial request (if using Fetch) or intercepts the initial request (if using Axios)
If a 402 response is received, parses the payment requirements from the PAYMENT-REQUIRED header
Creates a payment payload using the configured x402Client and registered schemes
Retries the request with the PAYMENT-SIGNATURE header

Prerequisites

Before you begin, ensure you have:

A crypto wallet with USDC (any EVM-compatible wallet, e.g., CDP Wallet, AgentKit)
Node.js and npm, Go, or Python and pip installed
A service that requires payment via x402
For testnet: Base Sepolia ETH for gas and testnet USDC. Get funds from the CDP Faucet

We have pre-configured examples available in our repo, including examples for fetch, Axios, and MCP.

1. Install Dependencies

Node.js
Go
Python

Install the x402 client packages:

# For fetch-based clients
npm install @x402/fetch @x402/evm

# For axios-based clients
npm install @x402/axios @x402/evm

# For Solana support, also add:
npm install @x402/svm

# For Bazaar discovery (optional):
npm install @x402/core @x402/extensions

Add the x402 Go module to your project:

go get github.com/x402-foundation/x402/go

Install the x402 package with your preferred HTTP client:

# For httpx (async) - recommended
pip install "x402[httpx]"

# For requests (sync)
pip install "x402[requests]"

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

2. Create a Wallet Client

Create a wallet client using a CDP Non-custodial Wallet (recommended) or a standalone wallet library (viem for EVM on Node.js, or Go’s crypto libraries).

Building with Embedded Wallets? If you’re building a user-facing application with embedded wallets, check out the X402 with CDP Wallets guide which shows how to use the useX402 hook for seamless payment integration.

CDP Non-custodial Wallet (Recommended)

First, create an account at cdp.coinbase.com and get the following API keys from the portal to store as environment variables:

# store in .env or using the command `export <name>="secret-info"`
CDP_API_KEY_ID=your-api-key-id
CDP_API_KEY_SECRET=your-api-key-secret
CDP_WALLET_SECRET=your-wallet-secret

Then, install the required packages:

Node.js

npm install @coinbase/cdp-sdk dotenv

Finally, instantiate the CDP client as suggested by the Non-custodial Wallet Quickstart:

Node.js

import { CdpClient } from "@coinbase/cdp-sdk";
import { toAccount } from "viem/accounts";
import dotenv from "dotenv";

dotenv.config();

const cdp = new CdpClient();
const cdpAccount = await cdp.evm.createAccount();
const signer = toAccount(cdpAccount);

Standalone Wallet Libraries

If you prefer to use your own wallet, you can use standalone libraries:

EVM (Node.js with viem)

npm install viem

import { privateKeyToAccount } from "viem/accounts";

// Create a signer from private key (use environment variable)
const signer = privateKeyToAccount(
  process.env.EVM_PRIVATE_KEY as `0x${string}`,
);

EVM (Go)

import (
    "crypto/ecdsa"
    "github.com/ethereum/go-ethereum/crypto"
)

// Load private key from environment
privateKey, _ := crypto.HexToECDSA(os.Getenv("EVM_PRIVATE_KEY"))

EVM (Python)

Install the required package:

pip install eth_account

Then instantiate the wallet signer:

import os
from eth_account import Account
from x402.mechanisms.evm import EthAccountSigner

account = Account.from_key(os.getenv("EVM_PRIVATE_KEY"))
signer = EthAccountSigner(account)

Solana (SVM)

Use SolanaKit to instantiate a signer:

import { createKeyPairSignerFromBytes } from "@solana/kit";
import { base58 } from "@scure/base";

// 64-byte base58 secret key (private + public)
const svmSigner = await createKeyPairSignerFromBytes(
  base58.decode(process.env.SOLANA_PRIVATE_KEY!),
);

3. Make Paid Requests Automatically

You can automatically handle 402 Payment Required responses and complete payment flows using the x402 helper packages.

Node.js
Go
Python (httpx)
Python (requests)

You can use either @x402/fetch or @x402/axios:

@x402/fetch
@x402/axios

@x402/fetch extends the native fetch API to handle 402 responses and payment headers for you. Full example here

import { x402Client, wrapFetchWithPayment, x402HTTPClient } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Create signer
const signer = privateKeyToAccount(process.env.EVM_PRIVATE_KEY as `0x${string}`);

// Create x402 client and register schemes
const client = new x402Client();
registerExactEvmScheme(client, { signer });

// Wrap fetch with payment handling
const fetchWithPayment = wrapFetchWithPayment(fetch, client);

// Make request - payment is handled automatically
const response = await fetchWithPayment("https://api.example.com/paid-endpoint", {
  method: "GET",
});

const body = await response.json();
console.log("Response:", body);

// Get payment receipt from response headers
if (response.ok) {
  const httpClient = new x402HTTPClient(client);
  const paymentResponse = httpClient.getPaymentSettleResponse(
    (name) => response.headers.get(name)
  );
  console.log("Payment settled:", paymentResponse);
}

Features:

Automatically handles 402 Payment Required responses
Verifies payment and generates PAYMENT-SIGNATURE headers
Retries the request with proof of payment
Supports all standard fetch options

@x402/axios adds a payment interceptor to Axios, so your requests are retried with payment headers automatically. Full example here

import { x402Client, withPaymentInterceptor, x402HTTPClient } from "@x402/axios";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";
import axios from "axios";

// Create signer
const signer = privateKeyToAccount(process.env.EVM_PRIVATE_KEY as `0x${string}`);

// Create x402 client and register schemes
const client = new x402Client();
registerExactEvmScheme(client, { signer });

// Create an Axios instance with payment handling
const api = withPaymentInterceptor(
  axios.create({ baseURL: "https://api.example.com" }),
  client,
);

// Make request - payment is handled automatically
const response = await api.get("/paid-endpoint");
console.log("Response:", response.data);

// Get payment receipt
const httpClient = new x402HTTPClient(client);
const paymentResponse = httpClient.getPaymentSettleResponse(
  (name) => response.headers[name.toLowerCase()]
);
console.log("Payment settled:", paymentResponse);

Features:

Automatically handles 402 Payment Required responses
Retries requests with payment headers
Exposes payment response in headers

Full example here

package main

import (
    "context"
    "encoding/json"
    "fmt"
    "net/http"
    "os"
    "time"

    x402 "github.com/x402-foundation/x402/go"
    evm "github.com/x402-foundation/x402/go/mechanisms/evm/exact/client"
)

func main() {
    privateKey := os.Getenv("EVM_PRIVATE_KEY")
    url := "http://localhost:4021/weather"

    // Create x402 client and register EVM scheme
    client := x402.NewX402Client()
    evm.RegisterExactEvmScheme(client, &evm.Config{
        PrivateKey: privateKey,
    })

    // Wrap HTTP client with payment handling
    httpClient := x402.WrapHTTPClient(client)

    // Make request - payment is handled automatically
    ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
    defer cancel()

    req, _ := http.NewRequestWithContext(ctx, "GET", url, nil)
    resp, err := httpClient.Do(req)
    if err != nil {
        fmt.Printf("Request failed: %v\n", err)
        return
    }
    defer resp.Body.Close()

    // Read response
    var data map[string]interface{}
    json.NewDecoder(resp.Body).Decode(&data)
    fmt.Printf("Response: %+v\n", data)

    // Check payment response header
    paymentHeader := resp.Header.Get("PAYMENT-RESPONSE")
    if paymentHeader != "" {
        fmt.Println("Payment settled successfully!")
    }
}

httpx provides async HTTP client support with automatic 402 payment handling.Full HTTPX example | Full Requests example

import asyncio
import os
from eth_account import Account

from x402 import x402Client
from x402.http import x402HTTPClient
from x402.http.clients import x402HttpxClient
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client


async def main() -> None:
    client = x402Client()
    account = Account.from_key(os.getenv("EVM_PRIVATE_KEY"))
    register_exact_evm_client(client, EthAccountSigner(account))

    http_client = x402HTTPClient(client)

    async with x402HttpxClient(client) as http:
        response = await http.get("https://api.example.com/paid-endpoint")
        await response.aread()

        print(f"Response: {response.text}")

        if response.is_success:
            settle_response = http_client.get_payment_settle_response(
                lambda name: response.headers.get(name)
            )
            print(f"Payment settled: {settle_response}")


asyncio.run(main())

requests provides sync HTTP client support with automatic 402 payment handling.Full Requests example

import os
from eth_account import Account

from x402 import x402ClientSync
from x402.http import x402HTTPClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client


def main() -> None:
    client = x402ClientSync()
    account = Account.from_key(os.getenv("EVM_PRIVATE_KEY"))
    register_exact_evm_client(client, EthAccountSigner(account))

    http_client = x402HTTPClientSync(client)

    with x402_requests(client) as session:
        response = session.get("https://api.example.com/paid-endpoint")

        print(f"Response: {response.text}")

        if response.ok:
            settle_response = http_client.get_payment_settle_response(
                lambda name: response.headers.get(name)
            )
            print(f"Payment settled: {settle_response}")


main()

Multi-Network Client Setup

You can register multiple payment schemes to handle different networks:

TypeScript
Go
Python

import { x402Client, wrapFetchWithPayment } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { registerExactSvmScheme } from "@x402/svm/exact/client";
import { privateKeyToAccount } from "viem/accounts";
import { createKeyPairSignerFromBytes } from "@solana/kit";
import { base58 } from "@scure/base";

// Create signers
const evmSigner = privateKeyToAccount(
  process.env.EVM_PRIVATE_KEY as `0x${string}`,
);
const svmSigner = await createKeyPairSignerFromBytes(
  base58.decode(process.env.SOLANA_PRIVATE_KEY!),
);

// Create client with multiple schemes
const client = new x402Client();
registerExactEvmScheme(client, { signer: evmSigner });
registerExactSvmScheme(client, { signer: svmSigner });

const fetchWithPayment = wrapFetchWithPayment(fetch, client);

// Now handles both EVM and Solana networks automatically!

import (
    x402 "github.com/x402-foundation/x402/go"
    x402http "github.com/x402-foundation/x402/go/http"
    evm "github.com/x402-foundation/x402/go/mechanisms/evm/exact/client"
    svm "github.com/x402-foundation/x402/go/mechanisms/svm/exact/client"
    evmsigners "github.com/x402-foundation/x402/go/signers/evm"
    svmsigners "github.com/x402-foundation/x402/go/signers/svm"
)

// Create signers
evmSigner, _ := evmsigners.NewClientSignerFromPrivateKey(os.Getenv("EVM_PRIVATE_KEY"))
svmSigner, _ := svmsigners.NewClientSignerFromPrivateKey(os.Getenv("SVM_PRIVATE_KEY"))

// Create client with multiple schemes
x402Client := x402.Newx402Client().
    Register("eip155:*", evm.NewExactEvmScheme(evmSigner)).
    Register("solana:*", svm.NewExactSvmScheme(svmSigner))

// Wrap HTTP client with payment handling
httpClient := x402http.WrapHTTPClientWithPayment(
    http.DefaultClient,
    x402http.Newx402HTTPClient(x402Client),
)

// Now handles both EVM and Solana networks automatically!

import asyncio
import os

from eth_account import Account

from x402 import x402Client
from x402.http.clients import x402HttpxClient
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client
from x402.mechanisms.svm import KeypairSigner
from x402.mechanisms.svm.exact.register import register_exact_svm_client


async def main() -> None:
    client = x402Client()

    # Register EVM scheme
    account = Account.from_key(os.getenv("EVM_PRIVATE_KEY"))
    register_exact_evm_client(client, EthAccountSigner(account))

    # Register SVM scheme
    svm_signer = KeypairSigner.from_base58(os.getenv("SVM_PRIVATE_KEY"))
    register_exact_svm_client(client, svm_signer)

    async with x402HttpxClient(client) as http:
        response = await http.get("https://api.example.com/paid-endpoint")
        print(f"Response: {response.text}")


asyncio.run(main())

Supporting the Upto Scheme

If you need to interact with services that use the upto payment scheme (usage-based billing), register the UptoEvmScheme alongside your existing exact schemes. The upto scheme is transparent to the buyer — the SDK handles the max-authorization signing automatically, and you are only charged the actual settled amount (which may be less than the authorized maximum).

TypeScript
Go
Python

import { x402Client } from "@x402/fetch";
import { ExactEvmScheme } from "@x402/evm/exact/client";
import { UptoEvmScheme } from "@x402/evm/upto/client";
import { privateKeyToAccount } from "viem/accounts";

const signer = privateKeyToAccount(process.env.EVM_PRIVATE_KEY as `0x${string}`);

const client = new x402Client();
client.register("eip155:*", new ExactEvmScheme(signer));
client.register("eip155:*", new UptoEvmScheme(signer));

import (
    x402 "github.com/x402-foundation/x402/go"
    exactevm "github.com/x402-foundation/x402/go/mechanisms/evm/exact/client"
    uptoevm "github.com/x402-foundation/x402/go/mechanisms/evm/upto/client"
    evmsigners "github.com/x402-foundation/x402/go/signers/evm"
)

evmSigner, _ := evmsigners.NewClientSignerFromPrivateKey(os.Getenv("EVM_PRIVATE_KEY"))

x402Client := x402.Newx402Client().
    Register("eip155:*", exactevm.NewExactEvmScheme(evmSigner)).
    Register("eip155:*", uptoevm.NewUptoEvmScheme(evmSigner))

import os
from eth_account import Account

from x402 import x402Client
from x402.http.clients import x402HttpxClient
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client
from x402.mechanisms.evm.upto import UptoEvmClientScheme

client = x402Client()
account = Account.from_key(os.getenv("EVM_PRIVATE_KEY"))
signer = EthAccountSigner(account)

register_exact_evm_client(client, signer)
client.register("eip155:*", UptoEvmClientScheme(signer))

The upto scheme is currently available on EVM networks only, in the TypeScript, Go, and Python SDKs. When registered, the SDK automatically selects the correct scheme based on what the server advertises in its 402 response.

4. Discover Available Services (Optional)

Instead of hardcoding endpoints, you can use the x402 Bazaar to dynamically discover available services. This is especially powerful for building autonomous agents that can find and use new capabilities.

Node.js
Go
Python

import { HTTPFacilitatorClient } from "@x402/core/http";
import { withBazaar } from "@x402/extensions/bazaar";

// Create facilitator client with Bazaar extension
const facilitatorClient = withBazaar(
  new HTTPFacilitatorClient({
    url: "https://api.cdp.coinbase.com/platform/v2/x402"
  })
);

// Query available services
const discovery = await facilitatorClient.extensions.discovery.listResources({
  type: "http",
  limit: 20,
});

// Filter services by criteria
const affordableServices = discovery.items.filter((item) =>
  item.accepts.some((req) => Number(req.amount) < 100000) // Under $0.10
);

console.log("Available services:", affordableServices);

import (
    "encoding/json"
    "net/http"
)

// Fetch available services
resp, _ := http.Get("https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources")
defer resp.Body.Close()

var services struct {
    Items []map[string]interface{} `json:"items"`
}
json.NewDecoder(resp.Body).Decode(&services)

fmt.Printf("Found %d services\n", len(services.Items))

import asyncio
import httpx


async def main() -> None:
    async with httpx.AsyncClient() as client:
        response = await client.get(
            "https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources",
            params={"type": "http", "limit": 20},
        )
        services = response.json()

        # Filter services by criteria
        affordable_services = [
            item for item in services.get("items", [])
            if any(int(req.get("amount", 0)) < 100000 for req in item.get("accepts", []))
        ]

        print(f"Available services: {affordable_services}")


asyncio.run(main())

Learn more about service discovery in the x402 Bazaar documentation, including how to filter services, understand their schemas, and build agents that can autonomously discover new capabilities.

CDP facilitator: For semantic search, quality-ranked results, and rich filters (network, asset, scheme, price, extensions, and more) without an API key, use GET https://api.cdp.coinbase.com/platform/v2/x402/discovery/search as documented in CDP Bazaar: semantic search. The examples above use the paginated /discovery/resources list, which is still appropriate when you want to page through the raw catalog.

5. Paying with Any ERC-20 Token via Permit2 (EVM)

Some endpoints accept payment in non-USDC ERC-20 tokens via Permit2. The official TypeScript, Go, and Python client SDKs handle Permit2 automatically — no extra client code is needed. When a server advertises Permit2 as the transfer method (extra.assetTransferMethod: "permit2"), the client SDK creates the correct PermitWitnessTransferFrom payload instead of an EIP-3009 authorization.

Gas Sponsorship (Automatic)

If the server declares a gas sponsorship extension (EIP-2612 or ERC-20), the TypeScript, Go, and Python client SDKs handle the Permit2 approval automatically:

EIP-2612 gas sponsoring: The client signs an off-chain permit() message. The facilitator submits the approval on-chain — no gas cost to you.
ERC-20 gas sponsoring: The client signs an approve() transaction. The facilitator broadcasts it on-chain before settling — no gas cost to you.

No additional client setup is needed for either case. The SDK detects the server’s advertised extension and responds accordingly.

One-Time Manual Approval (Fallback)

If the server uses Permit2 without gas sponsorship extensions, you must perform a one-time approval of the payment token to the Permit2 contract (0x000000000022D473030F116dDEE9F6B43aC78BA3) before your first payment. This only needs to be done once per token.

Node.js
Python

import { erc20Abi } from "viem";
import { walletClient } from "./your-wallet-setup";

await walletClient.writeContract({
  address: "0xYourTokenAddress",
  abi: erc20Abi,
  functionName: "approve",
  args: [
    "0x000000000022D473030F116dDEE9F6B43aC78BA3", // Permit2 contract
    BigInt("0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"), // max approval
  ],
});

from web3 import Web3
from eth_account import Account

w3 = Web3(Web3.HTTPProvider("https://sepolia.base.org"))
account = Account.from_key("0xYourPrivateKey")

PERMIT2_ADDRESS = "0x000000000022D473030F116dDEE9F6B43aC78BA3"
MAX_UINT256 = 2**256 - 1

token = w3.eth.contract(
    address=Web3.to_checksum_address("0xYourTokenAddress"),
    abi=[{
        "type": "function",
        "name": "approve",
        "inputs": [
            {"name": "spender", "type": "address"},
            {"name": "amount", "type": "uint256"},
        ],
        "outputs": [{"type": "bool"}],
        "stateMutability": "nonpayable",
    }],
)

tx = token.functions.approve(PERMIT2_ADDRESS, MAX_UINT256).build_transaction({
    "from": account.address,
    "nonce": w3.eth.get_transaction_count(account.address),
})

signed = account.sign_transaction(tx)
tx_hash = w3.eth.send_raw_transaction(signed.raw_transaction)
receipt = w3.eth.wait_for_transaction_receipt(tx_hash)
print(f"Approved Permit2: {tx_hash.hex()} (block {receipt['blockNumber']})")

After this one-time approval, all subsequent Permit2 payments for that token work automatically.

For full details on EVM transfer methods and gas sponsorship, see Network Support.

6. Error Handling

Clients will throw errors if:

No scheme is registered for the required network
The request configuration is missing
A payment has already been attempted for the request
There is an error creating the payment header

Common error handling:

try {
  const response = await fetchWithPayment(url, { method: "GET" });
  // Handle success
} catch (error) {
  if (error.message.includes("No scheme registered")) {
    console.error("Network not supported - register the appropriate scheme");
  } else if (error.message.includes("Payment already attempted")) {
    console.error("Payment failed on retry");
  } else {
    console.error("Request failed:", error);
  }
}

Summary

Install x402 client packages (@x402/fetch or @x402/axios) and mechanism packages (@x402/evm, @x402/svm)
Create a wallet signer
Create an x402Client and register payment schemes (exact for fixed-price, upto for usage-based billing)
Use the provided wrapper/interceptor to make paid API requests
(Optional) Use the x402 Bazaar to discover services dynamically
Payment flows are handled automatically for you — including upto where you only pay the actual usage

References:

@x402/fetch on npm
@x402/axios on npm
@x402/evm on npm
x402 Go module
x402 Python package on PyPI
x402 Bazaar documentation - Discover available services
X402 with CDP Wallets - User-facing applications with CDP wallets

For questions or support, join our Discord.

GET STARTED

WALLETS

PAYMENTS

STABLECOINS

TRADING

ONCHAIN TOOLS

WEBHOOKS

CUSTOMERS

CONSUMER APIS

BUSINESS APIS

INSTITUTIONAL APIS

Facilitator URLs

Prerequisites

1. Install Dependencies

2. Create a Wallet Client

CDP Non-custodial Wallet (Recommended)

Standalone Wallet Libraries

EVM (Node.js with viem)

EVM (Go)

EVM (Python)

Solana (SVM)

3. Make Paid Requests Automatically

Multi-Network Client Setup

Supporting the Upto Scheme

4. Discover Available Services (Optional)

5. Paying with Any ERC-20 Token via Permit2 (EVM)

Gas Sponsorship (Automatic)

One-Time Manual Approval (Fallback)

6. Error Handling

Summary

References:

​Facilitator URLs

​Prerequisites

​1. Install Dependencies

​2. Create a Wallet Client

​CDP Non-custodial Wallet (Recommended)

​Standalone Wallet Libraries

​EVM (Node.js with viem)

​EVM (Go)

​EVM (Python)

​Solana (SVM)

​3. Make Paid Requests Automatically

​Multi-Network Client Setup

​Supporting the Upto Scheme

​4. Discover Available Services (Optional)

​5. Paying with Any ERC-20 Token via Permit2 (EVM)

​Gas Sponsorship (Automatic)

​One-Time Manual Approval (Fallback)

​6. Error Handling

​Summary

​References:

Facilitator URLs

Prerequisites

1. Install Dependencies

2. Create a Wallet Client

CDP Non-custodial Wallet (Recommended)

Standalone Wallet Libraries

EVM (Node.js with viem)

EVM (Go)

EVM (Python)

Solana (SVM)

3. Make Paid Requests Automatically

Multi-Network Client Setup

Supporting the Upto Scheme

4. Discover Available Services (Optional)

5. Paying with Any ERC-20 Token via Permit2 (EVM)

Gas Sponsorship (Automatic)

One-Time Manual Approval (Fallback)

6. Error Handling

Summary

References: