WETH Skill

Wrap and unwrap ETH on Base and other EVM chains.

What is WETH?

WETH (Wrapped ETH) is an ERC20 version of ETH. You need it because:

•Many DeFi protocols only work with ERC20 tokens
•Uniswap V3 swaps require ERC20 tokens
•You can't use native ETH directly in most smart contracts

Contract Address (Base)

code

WETH: 0x4200000000000000000000000000000000000006

This is the same address on most L2s (Base, Optimism, Arbitrum).

Wrap ETH → WETH

Send ETH to the WETH contract's deposit() function:

javascript

import { encodeFunctionData, parseEther } from 'viem';

const WETH = '0x4200000000000000000000000000000000000006';

const txHash = await walletClient.sendTransaction({
  to: WETH,
  value: parseEther('0.1'), // Amount of ETH to wrap
  data: encodeFunctionData({
    abi: [{ name: 'deposit', type: 'function', inputs: [], outputs: [] }],
    functionName: 'deposit',
    args: []
  })
});

Or simply send ETH to the WETH address (it auto-wraps):

javascript

const txHash = await walletClient.sendTransaction({
  to: WETH,
  value: parseEther('0.1'),
});

Unwrap WETH → ETH

Call withdraw() to get your ETH back:

javascript

const txHash = await walletClient.sendTransaction({
  to: WETH,
  data: encodeFunctionData({
    abi: [{ 
      name: 'withdraw', 
      type: 'function', 
      inputs: [{ type: 'uint256' }], 
      outputs: [] 
    }],
    functionName: 'withdraw',
    args: [parseEther('0.1')] // Amount of WETH to unwrap
  })
});

Check Balances

javascript

// ETH balance
const ethBalance = await publicClient.getBalance({ address: walletAddress });

// WETH balance
const wethBalance = await publicClient.readContract({
  address: WETH,
  abi: [{
    name: 'balanceOf',
    type: 'function',
    inputs: [{ type: 'address' }],
    outputs: [{ type: 'uint256' }]
  }],
  functionName: 'balanceOf',
  args: [walletAddress]
});

When to Wrap vs Unwrap

Situation	Action
Need to swap on Uniswap	Wrap ETH → WETH first
Received WETH, want ETH for gas	Unwrap WETH → ETH
Sending to CEX	Usually unwrap (they want ETH)
DeFi protocols	Usually keep as WETH

Gas Considerations

•Wrapping: ~25,000 gas
•Unwrapping: ~30,000 gas
•On Base, this costs fractions of a cent

Keep some unwrapped ETH for gas fees!