Swap WETH

WETH is an ERC-20 token representing native ETH 1:1. It exists because ETH itself does not implement the ERC-20 transfer and allowance interface used by token contracts, liquidity pools and many DeFi applications.

The WETH contract mints one WETH for each ETH deposited and burns WETH when the corresponding ETH is withdrawn. Gas is paid separately, so it does not change the contract's 1:1 conversion amount.

Wrap ETH by calling deposit() and withdraw(amount); the contract converts both directions at 1:1. These are contract conversions, not liquidity-pool trades, so there is no pool fee, price impact or slippage—only network gas.

Leave enough native ETH outside the amount being wrapped to pay gas. An unwrap also requires native ETH before the transaction starts, which is what trips people up when a wallet holds WETH but has a zero ETH balance.

A wallet's "Convert" label should map an unwrap to the WETH contract's withdraw() function, not a DEX router.

Trade WETH for a different token through a DEX swap; withdraw() only returns native ETH. A route may use an automated market maker, and its liquidity-pool fee, network gas and price impact affect the result; quoted output can move before execution.

If the router lacks sufficient allowance, it may request a separate token approval. The approval transaction names the spender and amount, so those are the fields to compare with the intended route.

A swap quote should show the input and output contract addresses, active network, route, price impact and minimum received. Native ETH—not WETH—is still required to pay gas.

WETH and ETH are economically linked 1:1, but wallets and contracts handle them as different asset types. ETH is Ethereum's native currency and pays network gas; WETH is an ERC-20 token with transfer, approve and transferFrom functionality.

Keep enough ETH for gas and use it where a recipient explicitly expects native ETH. Use WETH where a protocol, pool or order requires an ERC-20 asset. A recipient that accepts ETH only is not specifying WETH.

Moving between canonical WETH and ETH is a 1:1 contract conversion rather than a market trade, although the transaction still costs gas.

Wrapping or unwrapping WETH has no conversion fee: the only cost is Ethereum network gas paid in native ETH. There is no universal gas amount because the fee depends on the network's current base fee, the transaction's gas use and any priority fee.

A DEX trade is different: it can include a liquidity-pool fee, network gas and price impact, while an approval may require its own transaction and gas. Price impact is not a network charge; it reduces execution relative to the pool's pre-trade price, which is why minimum received is the relevant output field.

Canonical WETH9 on Ethereum mainnet is 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2; the WETH contract record is the reference for matching that full address before signing. Its source is public and formally verified.

That does not authenticate every token, bridge asset, pool or application displaying the WETH ticker. Tickers and logos are copyable, and WETH-labelled assets on other networks can have different contracts or bridge assumptions.

Verify the active network, token contract, transaction target and approval spender. The canonical contract's safety does not remove routing, approval, phishing or wrong-network risk.

Most WETH failures come from the wrong network or token, insufficient native ETH for gas, a missing approval or choosing a DEX trade when withdraw() is the required action.

• Cannot unwrap: the fix is canonical WETH on the active network, ETH available for gas and withdraw() rather than a swap router.
• Token is missing: add it using the verified contract address on the correct network; the ticker alone does not identify the token.
• Approval keeps appearing: compare the earlier approval's confirmation, network, router and amount with the current request.
• Swap reverted: common causes include an expired quote, insufficient allowance or balance, changed pool conditions, or a slippage limit that the route can no longer satisfy.
• Received WETH instead of ETH: the route delivered the ERC-20 token. Use withdraw() in a separate transaction if native ETH is what the destination requires.