> ## Documentation Index > Fetch the complete documentation index at: https://circle-devdocs-test-ai-codegen-component.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # Quickstart: Set up and transfer USDC on EVM chains USDC provides the ability to transfer digital dollars over public blockchains using smart contracts. The smart contract allows you to send, receive, and store digital dollars onchain with a wallet. This guide demonstrates how to use the [viem](https://viem.sh/) framework to build a simple app that enables a user to connect their wallet and interact with the blockchain by sending a USDC transaction from their wallet address. ## Prerequisites Before you start building the sample app to perform a USDC transfer, ensure you meet the following prerequisites: 1. Node.js and npm are installed. You can [download and install Node.js directly](https://nodejs.org), or use a version manager like [nvm](https://github.com/nvm-sh/nvm). The npm binary comes with Node.js. 2. MetaMask is installed. You can [download and install MetaMask](https://metamask.io) from their website. When performing initial setup, you should create a wallet for the Ethereum Sepolia testnet. 3. You have testnet native tokens and testnet USDC in your wallet. You can get Sepolia ETH (native token) from a [public faucet](https://cloud.google.com/application/web3/faucet/ethereum/sepolia) and you can get Sepolia USDC from the [Circle Faucet](https://faucet.circle.com). ## Project setup To begin building the sample app, first set up your project environment and install dependencies. Create a new project directory and initialize a project in it: ```shell Shell theme={null} mkdir usdc-transfer-app cd usdc-transfer-app npm init -y ``` In your project directory, install the required dependencies: ```shell Shell theme={null} npm install react@^18.2.0 \ react-dom@^18.2.0 \ @types/react@^18.0.27 \ @types/react-dom@^18.0.10 \ @vitejs/plugin-react@^3.1.0 \ typescript@^5.0.3 \ vite@^4.4.5 ``` This sets up your development environment with the necessary libraries and tools for building a React app with TypeScript and Vite. Finally, install viem: ```shell Shell theme={null} npm install viem ``` ## Building the transfer app The following sections outline the relevant business logic of the example app. You can view the [full source for the app](#full-source) in the final section of this guide. ### Set up public client The public client interacts with the blockchain network. In this example, you should specify the Ethereum Sepolia network. ```typescript Typescript theme={null} import { http, createPublicClient } from "viem"; import { sepolia } from "viem/chains"; const publicClient = createPublicClient({ chain: sepolia, transport: http(), }); ``` ### Set up wallet client The wallet client interacts with Ethereum accounts to retrieve balances, execute transactions, and sign messages. ```typescript Typescript theme={null} import { createWalletClient } from "viem"; import { sepolia } from "viem/chains"; const walletClient = createWalletClient({ chain: sepolia, transport: custom(window.ethereum!), }); ``` ### Define USDC contract details Define the USDC contract address and the application binary interface (ABI). The ABI specifies the functions available on the smart contract. Note that the USDC token contract address varies by blockchain. This example uses the Ethereum Sepolia contract address. See [USDC Contract Addresses](/stablecoins/usdc-contract-addresses) for a full list of addresses for the USDC smart contract. ```typescript Typescript theme={null} const USDC_CONTRACT_ADDRESS = "0x1c7D4B196Cb0C7B01d743Fbc6116a902379C7238"; const USDC_ABI = [ { constant: false, inputs: [ { name: "_to", type: "address" }, { name: "_value", type: "uint256" }, ], name: "transfer", outputs: [{ name: "", type: "bool" }], type: "function", }, ]; ``` ### Connect wallet Create a function to connect to the user's wallet in MetaMask and retrieve the wallet address. ```typescript Typescript theme={null} const connect = async () => { const [address] = await walletClient.requestAddresses(); setAccount(address); }; ``` ### Send transaction Create a function to send the USDC transfer transaction. This function encodes the transfer function data and sends the transaction to the blockchain using the wallet client. ```typescript Typescript theme={null} const data = encodeFunctionData({ abi: USDC_ABI, functionName: "transfer", args: [to, valueInWei], }); const hash = await walletClient.sendTransaction({ account, to: USDC_CONTRACT_ADDRESS, data, }); ``` ### Wait for transaction receipt Use the public client to wait for the transaction receipt, which confirms that the transaction was included in a block. ```typescript Typescript theme={null} useEffect(() => { (async () => { if (hash) { const receipt = await publicClient.waitForTransactionReceipt({ hash }); setReceipt(receipt); } })(); }, [hash]); ``` ## Full source Now that you understand the core steps for programmatically performing a USDC transaction, create an `index.tsx` and `index.html` file in your project directory and populate them with the sample code below. This app enables you to send USDC tokens from one wallet to another. The source wallet must contain native testnet tokens (to pay for gas fees) and testnet USDC. `index.tsx` ```typescript Typescript theme={null} import React, { useEffect, useState } from 'react'; import ReactDOM from 'react-dom/client'; import { http, type Address, type Hash, type TransactionReceipt, createPublicClient, createWalletClient, custom, stringify, encodeFunctionData, } from 'viem'; import { sepolia } from 'viem/chains'; import 'viem/window'; const publicClient = createPublicClient({ chain: sepolia, transport: http() }); const walletClient = createWalletClient({ chain: sepolia, transport: custom(window.ethereum!) }); const USDC_CONTRACT_ADDRESS = '0x1c7D4B196Cb0C7B01d743Fbc6116a902379C7238'; const USDC_ABI = [ { constant: false, inputs: [ { name: '_to', type: 'address' }, { name: '_value', type: 'uint256' }, ], name: 'transfer', outputs: [{ name: '', type: 'bool' }], type: 'function', }, ]; function Example() { const [account, setAccount] = useState
(); const [hash, setHash] = useState(); const [receipt, setReceipt] = useState(); const addressInput = React.createRef(); const valueInput = React.createRef(); const connect = async () => { const [address] = await walletClient.requestAddresses(); setAccount(address); }; const sendTransaction = async () => { if (!account) return; const to = addressInput.current!.value as Address; const value = valueInput.current!.value as `${number}`; const valueInWei = BigInt(value) * BigInt(10 ** 6); // Assuming USDC has 6 decimals const data = encodeFunctionData({ abi: USDC_ABI, functionName: 'transfer', args: [to, valueInWei], }); const hash = await walletClient.sendTransaction({ account, to: USDC_CONTRACT_ADDRESS, data, }); setHash(hash); }; useEffect(() => { (async () => { if (hash) { const receipt = await publicClient.waitForTransactionReceipt({ hash }); setReceipt(receipt); } })(); }, [hash]); if (account) { return ( <>
Connected: {account}
{receipt && (
Receipt: 
{stringify(receipt, null, 2)}
)} ); } return ; } ReactDOM.createRoot(document.getElementById('root') as HTMLElement).render( ); ``` `index.html` ```html HTML theme={null} USDC Transfer Sample App

USDC Transfer Sample App

``` These two source files provide a complete demonstration app that you can use to perform a USDC transfer from a MetaMask wallet. When you open the app, you can connect your wallet, input the recipient address, and click **Send** to execute the transaction on Ethereum Sepolia. The app provides a transaction receipt once the transaction is included in a block. ### Screenshots Wallet connect screen: Transfer screen: