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Overview

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Supported Facilitators

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x402.org Facilitator

• Supports: Base Sepolia
• Notes: Recommended for testing and development. This is the default facilitator in the x402 packages and requires no setup.
• URL: https://x402.org/facilitator

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CDP’s x402 Facilitator

• Supports: Base, Base Sepolia
• Notes: Production-ready for mainnet payments with KYT/OFAC compliance checks. Can also be used for testing on Base Sepolia. Requires CDP API keys. Uses facilitator object instead of facilitator URL.
• Requirements: CDP account and API keys from cdp.coinbase.com, see Quickstart for Sellers: Running on Mainnet for more details.

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x402.rs Facilitator

• Supports: Base Sepolia, Base, XDC Mainnet
• Notes: Rust-based facilitator operated by the x402 community.
• URL: https://facilitator.x402.rs

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Self-Hosted Facilitators

• Supports: Any EVM network
• Notes: Run your own facilitator for full control and customization. Supports networks like Avalanche, Polygon, Arbitrum, and other EVM-compatible chains.
• Setup: See “Adding Support for New Networks” section below

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Third-Party Facilitators

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Token Support

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EIP-3009 Requirement

• Gasless transfers: The facilitator sponsors gas fees
• Signature-based authorization: Users sign transfer authorizations off-chain
• Secure payments: Transfers are authorized by cryptographic signatures

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Specifying Payment Amounts

1. Price String (e.g., "$0.01") - The system infers USDC as the token
2. TokenAmount - Specify exact atomic units of any EIP-3009 token

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Using Custom EIP-3009 Tokens

1. Token Address: The contract address of your EIP-3009 token
2. EIP-712 Name: The token’s name for EIP-712 signatures
3. EIP-712 Version: The token’s version for EIP-712 signatures

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Finding Token Information on Basescan

1. Name: Read the name() function - Example on Basescan
2. Version: Read the version() function - Example on Basescan

{
  eip712: {
    name: "USD Coin",    // From name() function
    version: "2"         // From version() function
  }
}

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USDC - The Default Token

• Status: Supported by default across all networks
• Why: USDC implements EIP-3009 and is widely available
• Networks: Available on Base, Base Sepolia, and all supported networks

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Why EIP-3009?

1. Gas abstraction: Buyers don’t need native tokens (ETH, MATIC, etc.) for gas
2. One-step payments: No separate approval transactions required
3. Universal facilitator support: Any EIP-3009 token works with any facilitator

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Quick Reference

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Adding Support for New Networks

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Option 1: Contributing to x402 Packages

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Files to Modify

1. typescript/packages/x402/src/types/shared/evm/config.ts Add your network’s chain ID and USDC address:
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   Ask AI

   // Example: Adding Avalanche networks
   "43113": {  // Avalanche Fuji testnet chain ID
     usdcAddress: "0x5425890298aed601595a70AB815c96711a31Bc65",
     usdcName: "USD Coin",
   },
   "43114": {  // Avalanche mainnet chain ID
     usdcAddress: "0xB97EF9Ef8734C71904D8002F8b6Bc66Dd9c48a6E",
     usdcName: "USDC",
   },
   

2. typescript/packages/x402/src/types/shared/network.ts Add your network to the schema and mappings:
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   // Update the NetworkSchema enum
   export const NetworkSchema = z.enum(["base-sepolia", "base", "avalanche-fuji", "avalanche"]);
   
   // Add to SupportedEVMNetworks array
   export const SupportedEVMNetworks: Network[] = [
     "base-sepolia",
     "base",
     "avalanche-fuji",
     "avalanche",
   ];
   
   // Add to EvmNetworkToChainId mapping
   ["avalanche-fuji", 43113],
   ["avalanche", 43114],
   

3. typescript/packages/x402/src/types/shared/evm/wallet.ts - Update getChainFromNetwork function Add your network to the getChainFromNetwork function to map your network string to the viem chain object:
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   import { avalanche, avalancheFuji } from "viem/chains";
   
   // Add your network to the switch statement in getChainFromNetwork
   case "avalanche":
     return avalanche;
   case "avalanche-fuji":
     return avalancheFuji;
   

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Key Requirements

• Network key: Use a consistent network identifier (e.g., avalanche-fuji) across all files
• Viem chain: Your network must be available in viem/chains or you’ll need to define it manually
• USDC address: Must be EIP-3009 compatible (has transferWithAuthorization function)
• Chain ID: Use your network’s official chain ID in the config
• Consistency: Ensure the network name matches across NetworkSchema, SupportedEVMNetworks, EvmNetworkToChainId, and the getChainFromNetwork switch statement

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Option 2: Running Your Own Facilitator

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Prerequisites

1. Access to an RPC endpoint for your target network
2. A wallet with native tokens for gas sponsorship
3. The x402 facilitator code

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Future Network Support

• Additional L2 networks
• Non-EVM chain support (Solana in development)
• Cross-chain payment capabilities

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Getting Help

• Join the x402 Discord community
• Check the x402 GitHub repository

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Summary

• Base and Base Sepolia have the best out-of-the-box support
• Any EVM network can be supported with a custom facilitator
• Any EIP-3009 token (with transferWithAuthorization) works on any facilitator
• Use price strings for USDC or TokenAmount for custom tokens
• Network choice affects gas costs and payment economics

• Quickstart for Sellers — Start accepting payments on supported networks
• Core Concepts — Learn how x402 works under the hood
• Facilitator — Understand the role of facilitators
• MCP Server — Set up AI agents to use x402 payments