Sending USDC (or other ERC-20s)

Sending USDC, or other ERC-20 tokens, is one of the most common actions taken by wallet users on Ethereum-based chains. This guide will walk you through how to format the transaction input data for these tokens, using USDC as an example.

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1. Get the USDC contract address

To send USDC, you’ll need the contract address for USDC. The address is different for each network, so make sure you get the correct address for the network you’re targeting. You can go to Circle’s website to look up the USDC address on both main networks and test networks.

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2. Format the transaction send input data

USDC, and other ERC-20 tokens, are smart contracts. In order to send these tokens, your transaction needs to call the transfer function on the contract, which takes in two parameters:

• to: The address of the recipient
• value: The amount of tokens to send

When formatting the transaction input data, you must define the expected interface of the function you’re calling by providing an ABI. You can use helper packages like viem to provide the ABI and encode the function parameters.

Additionally, each ERC-20 token defines a decimals value, which is the number of decimal places for the token. For USDC, the decimals value is usually 6, but for most other ERC-20 tokens, it’s 18.

npm install viem

import {encodeFunctionData, erc20Abi} from 'viem';

const recipientAddress = '0x...';
const amountToSend = 1; // Sender wants to send 1 USDC
const decimals = 6; // USDC has 6 decimals

const encodedData = encodeFunctionData({
  abi: erc20Abi,
  functionName: 'transfer',
  args: [recipientAddress, amountToSend * 10 ** decimals]
});

npm install viem

import {encodeFunctionData, erc20Abi} from 'viem';

const recipientAddress = '0x...';
const amountToSend = 1; // Sender wants to send 1 USDC
const decimals = 6; // USDC has 6 decimals

const encodedData = encodeFunctionData({
  abi: erc20Abi,
  functionName: 'transfer',
  args: [recipientAddress, amountToSend * 10 ** decimals]
});

pip install eth-abi

from eth_abi.abi import encode
from eth_utils import function_signature_to_4byte_selector

usdc_address = "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913" # address on base
# Simplified ABI for the transfer function only
function_signature = "transfer(address,uint256)"
function_selector = function_signature_to_4byte_selector(function_signature)
decimals = 6
encoded_params = encode(
    ["address", "uint256"],
    [recipient_address, amount_to_send * 10**decimals],
)
data = "0x" + (function_selector + encoded_params).hex()

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3. Send the transaction

You can send the transaction using the Privy API. Below are examples for React, React Native, and NodeJS; you can find other SDKs’ send transaction examples in the Send a transaction guide.

import { useSendTransaction } from '@privy-io/react-auth';
const { sendTransaction } = useSendTransaction();

const { hash } = await sendTransaction({
to: usdcContractAddress,
data: encodedData, // from the previous step
chainId: 8453, // Base's chainId
})

import { useSendTransaction } from '@privy-io/react-auth';
const { sendTransaction } = useSendTransaction();

const { hash } = await sendTransaction({
to: usdcContractAddress,
data: encodedData, // from the previous step
chainId: 8453, // Base's chainId
})

import {useEmbeddedEthereumWallet} from '@privy-io/expo';

const {wallets} = useEmbeddedEthereumWallet();
const wallet = wallets[0];

const provider = await wallet.getProvider();
const accounts = await provider.request({
    method: 'eth_requestAccounts',
});

// Send transaction (will be signed and populated)
const response = await provider.request({
    method: 'eth_sendTransaction',
    params: [
        {
            from: accounts[0],
            to: usdcContractAddress,
            data: encodedData, // from the previous step
        },
    ],
});

const usdcContractAddress = '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913'; // on Base

const {hash} = await privy.walletApi.ethereum.sendTransaction({
walletId: 'insert-wallet-id',
caip2: 'eip155:8453', // Base's caip2
to: usdcContractAddress,
data: encodedData // from the previous step
})

tx = client.wallets.rpc(
    wallet_id=user.wallet_id,
    method="eth_sendTransaction",
    caip2="eip155:8453", # Base's caip2
    params={
        "transaction": {
            "to": usdc_address,
            "data": data,
        },
    },
)
return {"response": tx.data}

# response should look like this:
# {
# "caip2": "eip155:8453",
# "hash": "0x6443ca5b9ac1aeb31ec56e81e90699a08ef4f5d4b799855c5216a06a9f349f9e",
# "transaction_id": "kjrw3noey7m5q2l5tter50sl"
# }

You’ve successfully sent USDC!