Network Support

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Network Identifiers (CAIP-2)

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CAIP-2 Format

• EVM Networks: eip155:{chainId} where chainId is the EVM chain ID
• Solana Networks: solana:{genesisHash} where genesisHash is a truncated genesis hash

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Examples

// EVM networks
network: "eip155:8453"      // Base mainnet (chain ID 8453)
network: "eip155:84532"     // Base Sepolia (chain ID 84532)
network: "eip155:137"       // Polygon mainnet (chain ID 137)
network: "eip155:1"         // Ethereum mainnet (chain ID 1)

// Solana networks
network: "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp"  // Solana mainnet
network: "solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1"  // Solana devnet

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Reference SDK Support

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EVM Support (@x402/evm)

• EIP-3009 (Transfer With Authorization): For tokens that natively implement EIP-3009, such as USDC and EURC. The buyer signs an off-chain authorization and the facilitator submits the transfer — no on-chain approval needed.
• Permit2: For any ERC-20 token, using Permit2 as a universal token approval mechanism. The buyer signs a PermitWitnessTransferFrom message and the facilitator executes the transfer.

• Any Ethereum L1 or L2
• Any EVM-compatible chain with a valid chain ID
• Any ERC-20 token (via Permit2) or EIP-3009 compliant token (USDC, EURC, etc.)

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Permit2 Approval

• EIP-2612 gas sponsoring: For tokens that implement EIP-2612 (permit), the facilitator can sponsor the Permit2 approval on-chain using a signed off-chain permit message — no gas required from the buyer.
• ERC-20 gas sponsoring: For generic ERC-20 tokens without EIP-2612 support, the facilitator can sponsor the Permit2 approval transaction on the buyer’s behalf.

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Solana Support (@x402/svm)

• SPL Token Program tokens
• Token2022 program tokens

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Other SDKs

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CDP Facilitator Support

• Mainnet: https://api.cdp.coinbase.com/platform/v2/x402
  • Requires CDP API keys
  • Supports: Base, Polygon, Solana

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x402.org Testnet Facilitator

• No API key required
• For testnet use only

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Other Facilitators

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Chain ID Reference

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Token Support

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EVM Networks

• EIP-3009 tokens (e.g., USDC, EURC): Use EIP-3009 (Transfer With Authorization) for fully gasless transfers where the buyer signs an off-chain message and the facilitator submits the transaction. No on-chain approval step is needed.
• Generic ERC-20 tokens: Use Permit2 for transfers. The buyer must have an approval to the Permit2 contract, which can be handled via gas sponsorship extensions (EIP-2612 or ERC-20 gas sponsoring) or a one-time manual approval.

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Solana Networks (SPL / Token2022)

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Price Formatting

// Dollar string format (recommended for readability)
price: "$0.001"    // 0.001 USDC
price: "$1.00"     // 1 USDC
price: "$0.50"     // 0.50 USDC

// Atomic units (for precision)
amount: "1000"     // 0.001 USDC (6 decimals)
amount: "1000000"  // 1 USDC (6 decimals)

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Usage Examples

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Server-Side Configuration

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

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

// Register scheme for Base Sepolia
const server = new x402ResourceServer(facilitatorClient)
  .register("eip155:84532", new ExactEvmScheme());

app.use(
  paymentMiddleware(
    {
      "GET /api": {
        accepts: [
          {
            scheme: "exact",
            price: "$0.001",
            network: "eip155:84532", // Base Sepolia
            payTo: "0xYourAddress",
          },
        ],
        description: "API endpoint",
      },
    },
    server,
  ),
);

import (
    x402 "github.com/coinbase/x402/go"
    x402http "github.com/coinbase/x402/go/http"
    evm "github.com/coinbase/x402/go/mechanisms/evm/exact/server"
)

network := x402.Network("eip155:84532") // Base Sepolia

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

​

Using a Custom Network

// Example: Using Ethereum mainnet with a custom facilitator
const facilitatorClient = new HTTPFacilitatorClient({
  url: "https://example.facilitator.com",
});

const server = new x402ResourceServer(facilitatorClient)
  .register("eip155:1", new ExactEvmScheme()); // Ethereum mainnet

app.use(
  paymentMiddleware(
    {
      "GET /api": {
        accepts: [
          {
            scheme: "exact",
            price: "$0.001",
            network: "eip155:1",
            payTo: "0xYourAddress",
            asset: "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48", // USDC on Ethereum
          },
        ],
        description: "API endpoint",
      },
    },
    server,
  ),
);

​

Multi-Network Support

{
  "GET /api": {
    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: "Multi-network endpoint",
  },
}

​

Running Your Own Facilitator

1. Use the reference implementation: The x402 GitHub repository contains facilitator code
2. Use a community implementation: Check the x402 Ecosystem for self-hostable options

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Next Steps

• Quickstart for Sellers - Start accepting payments
• Quickstart for Buyers - Start making payments
• Core Concepts: Facilitator - Learn about facilitators
• x402 Ecosystem - Explore facilitators and tools