How to Send Ethereum ERC20 Tokens Using ethers.js

Sending tokens is a fundamental feature of any Ethereum wallet. This guide walks through the essential steps of integrating ERC20 token transfer functionality using the ethers.js library, covering contract interaction, balance checks, and secure transaction execution.

Understanding ERC20 Tokens and ABI

ERC20 tokens are standardized smart contracts on the Ethereum blockchain. To interact with them, you need the Application Binary Interface (ABI), which defines the contract's methods and structures.

The ERC20 Interface Standard

The ERC20 standard includes these core functions:

function balanceOf(address tokenOwner) public view returns (uint balance);
function transfer(address to, uint tokens) public returns (bool success);
function approve(address spender, uint tokens) public returns (bool success);
function transferFrom(address from, address to, uint tokens) public returns (bool success);

Obtaining Contract ABI

The ABI is typically generated when compiling a smart contract. Development environments like Remix IDE allow you to easily copy the ABI JSON array after compilation.

A typical function entry in the ABI includes:

name: The function name
type: Function type (function, constructor, fallback, or event)
inputs: Array of input parameters with names and types
outputs: Array of output parameters
constant: Boolean indicating if the function modifies state
payable: Boolean indicating if the function can receive Ether

Initializing the Contract Object

Once you have the ABI and contract address, initialize the contract object:

const abi = [...]; // Your ABI array
const contractAddress = "0x..."; // Token contract address
const provider = new ethers.providers.Web3Provider(window.ethereum);
const tokenContract = new ethers.Contract(contractAddress, abi, provider);

The contract address is deployed on the Ethereum network and unique to each token.

Checking Token Balances

Before transferring tokens, users need to check their balance. Implement a simple UI with an input field to display balances:

<label>Token Balance:</label>
<input type="text" id="tokenBalance" readonly>

Retrieve and display the balance using:

const balanceElement = document.getElementById('tokenBalance');
tokenContract.balanceOf(walletAddress)
  .then(balance => {
    balanceElement.value = ethers.utils.formatUnits(balance, decimals);
  })
  .catch(error => console.error('Balance check failed:', error));

Executing Token Transfers

Token transfers require creating and signing transactions. Implement a transfer form:

<h3>Transfer Tokens</h3>
<label>Recipient Address:</label>
<input type="text" id="recipientAddress">
<label>Amount:</label>
<input type="number" id="transferAmount">
<button id="transferButton">Send Tokens</button>

Transaction Execution Logic

The transfer process involves several key steps:

document.getElementById('transferButton').addEventListener('click', async () => {
  const recipient = ethers.utils.getAddress(document.getElementById('recipientAddress').value);
  const amount = document.getElementById('transferAmount').value;
  const signer = provider.getSigner();
  const contractWithSigner = tokenContract.connect(signer);
  
  try {
    // Estimate gas requirements
    const gasEstimate = await contractWithSigner.estimateGas.transfer(recipient, amount);
    
    // Execute transfer
    const transaction = await contractWithSigner.transfer(recipient, amount, {
      gasLimit: gasEstimate,
      gasPrice: ethers.utils.parseUnits("2", "gwei")
    });
    
    console.log('Transaction hash:', transaction.hash);
    
    // Wait for confirmation
    await transaction.wait();
    console.log('Transfer confirmed');
    
  } catch (error) {
    console.error('Transfer failed:', error);
  }
});

Key Considerations

Always validate addresses using ethers.utils.getAddress()
Connect a signer to the contract for state-changing operations
Gas estimation helps prevent failed transactions but isn't mandatory
Use appropriate gas prices based on network conditions

👉 Explore advanced transaction strategies

Security Best Practices

When implementing token transfers:

Validate addresses - Ensure recipient addresses are valid Ethereum addresses
Handle errors gracefully - Provide clear error messages for failed transactions
Confirm large transactions - Implement additional confirmation for significant transfers
Monitor gas prices - Adjust gas prices based on network congestion
Test thoroughly - Always test with testnet tokens before mainnet deployment

Frequently Asked Questions

What is the difference between transferring ETH and ERC20 tokens?
ETH is the native currency transferred directly between addresses, while ERC20 token transfers involve calling a smart contract function that updates internal balance mappings. The gas requirements and processes differ significantly.

Why do I need to estimate gas for token transfers?
Gas estimation calculates the computational effort required for the transaction. While optional, it helps set appropriate gas limits and prevents failed transactions due to insufficient gas.

Can I transfer tokens without a signer?
No. Any operation that changes blockchain state requires a signed transaction. Read-only operations like balance checks can be performed with just a provider connection.

What happens if a token transfer fails?
Failed transactions still consume gas but don't transfer tokens. The transaction will revert any state changes, and you'll need to resubmit with corrected parameters.

How do I handle different token decimals?
Tokens have varying decimal places (0-18). Always format amounts using ethers.utils.formatUnits(value, decimals) for display and parseUnits for transaction parameters.

Why is address validation important?
Invalid addresses can lead to irreversible token loss. Always validate and checksum addresses using Ethereum's address validation utilities.

Conclusion

Implementing ERC20 token transfers requires understanding smart contract interaction, transaction signing, and gas management. The ethers.js library provides comprehensive tools for these operations, enabling secure and efficient token transfer functionality in Web3 applications. Always prioritize security validation and user experience when implementing financial operations.

Remember to test thoroughly on test networks before deploying wallet functionality to production environments, and keep abreast of evolving best practices in smart contract interaction.