Ethereum Mainnet Joins RelAI - Gas-Sponsored x402 Payments on the World's Largest Smart Contract Platform

Ethereum mainnet is now live on the RelAI Facilitator. Developers can monetize APIs with USDC micropayments on Ethereum - and their users never pay a single wei in gas.

The Ethereum Challenge

Ethereum is the most trusted, most liquid, and most widely adopted smart contract platform. But gas fees have always been the elephant in the room. A simple ERC-20 transfer can cost $2–10 depending on network congestion - making micropayments for API calls economically impossible.

Until now.

RelAI Solves the Gas Problem

With RelAI as your x402 facilitator, gas fees are completely invisible to end users. Here's what happens under the hood:

1. Your API returns HTTP 402 with x402 v2 payment requirements
2. The user's wallet signs an EIP-3009 transferWithAuthorization - a gasless off-chain signature
3. RelAI's backend wallet submits the transaction and pays ETH for gas
4. USDC moves from the user to the merchant in a single atomic transaction
5. The user receives the API response - zero gas, zero friction

Why This Matters

For API Developers

• Tap into the largest USDC liquidity pool - Ethereum holds more USDC than any other chain
• Reach the widest audience - every crypto wallet supports Ethereum
• Premium positioning - Ethereum mainnet signals trust and permanence

For End Users

• Zero gas costs - RelAI absorbs all ETH gas fees
• One-click payments - sign once, get access instantly
• Use any wallet - MetaMask, Phantom, Coinbase Wallet, WalletConnect, or a custodial RelAI wallet

Technical Details

The EIP-3009 Advantage

All RelAI EVM payments use EIP-3009 transferWithAuthorization - not EIP-2612 permit. This is a deliberate choice:

• Atomic transfer - tokens move in a single contract call, no separate approve + transferFrom
• Random nonces - bytes32 random nonces eliminate ordering dependencies and replay risks
• Purpose-built - EIP-3009 was designed by Circle specifically for delegated USDC transfers
• Consistent across chains - the same signing flow works on Ethereum, Polygon, Base, Avalanche, and SKALE

Getting Started

1. Configure Your API

{
  network: 'ethereum',
  facilitator: 'relai',
  pricing: {
    'GET /premium-data': { amount: '100000' }  // $0.10 in USDC
  }
}

2. Frontend Integration with RelAI SDK

import { createRelaiClient } from '@relai-fi/x402'
const client = createRelaiClient({
  evmWallet: {
    address: userAddress,
    signTypedData: wallet.signTypedData,
  }
})
// That's it  - the SDK handles 402 detection, signing, and payment
const response = await client.fetch('https://your-api.com/premium-data')

3. Or Use a Custodial Wallet

Users who don't have their own wallet can use RelAI's built-in custodial wallets. Fund the wallet with USDC, and payments happen automatically - no browser extension required.

The Full RelAI Network

Ethereum joins a growing list of supported networks:

When to Use Ethereum vs Other Networks

• Ethereum - highest trust, largest USDC pool, premium APIs, institutional users
• Polygon - high volume, low-cost APIs, gaming, social
• Base - Coinbase ecosystem, consumer apps
• SKALE - zero gas costs (even for RelAI), maximum throughput
• Solana - sub-second finality, DeFi integrations

Start Building

Ethereum mainnet support is live now. If you're already using RelAI on other networks, just set network: 'ethereum' - everything else stays the same.

New to RelAI? Check out our quickstart guide or explore the API playground to see x402 payments in action.