Swap WETH.

To Swap WETH means exchanging wrapped ETH for another ERC-20 token inside a decentralized exchange pool, with the trade priced by the pool's own reserves rather than a central order book. A pool is a pair of tokens locked in a smart contract; when you swap, you deposit one side and the contract releases the other according to its pricing formula. Because that formula and the surrounding contract code assume ERC-20 behavior throughout, the asset sitting on the ETH side of almost every pool is WETH, not native ETH. Front-end wallets quietly wrap your ETH or unwrap WETH at the edges of the transaction, which is why most people never notice the token swap happening beneath their trade.

WETH versus ETH in a trade

Native ETH moves value through the protocol's own transfer mechanism and carries no token contract, so a pool contract cannot hold it directly. WETH solves that by locking ETH 1:1 in a deposit contract and minting an ERC-20 that behaves exactly like any other token on the pair side of a pool.

When your wallet already holds WETH

If a prior transaction left WETH sitting in your wallet, a swap skips the wrap step entirely and goes straight to the trade, which saves one transaction and its gas. If your wallet holds native ETH instead, most interfaces wrap it for you in the same flow, so the practical difference shows up mainly in gas cost, not in how you set up the trade.

Automated market maker contracts need a balance they can read, hold, and move with ordinary token calls, and the ERC-20 interface defined on ethereum.org gives them exactly that. Native ETH has no such interface, so every major decentralized exchange pairs its tokens against WETH rather than ETH directly. This is a structural detail, not a limitation: it is the reason a router can quote, route through, and settle an ETH-denominated trade with the same code path it uses for any other token pair.

The wrap-unwrap convenience layer

Interfaces hide this by auto-wrapping ETH on the way in and auto-unwrapping WETH on the way out, so a person who only ever clicks "ETH" in a dropdown still ends up trading the wrapped token inside the pool itself.

The most common reason to Swap WETH is moving into a stablecoin like USDC or USDT to lock in a price, or into another project's token to take a position. Each route runs through one or more pools, and the pool you land in determines your price, your fee, and how much the trade moves the market against you. The table below compares the shapes of route you will typically choose between.

Route type	Typical use	Trade-off
Single pool, high liquidity	WETH to major stablecoin	Tight price, lowest price impact
Multi-hop route	WETH to a smaller token	Slightly higher cost, better final price
Split across pools	Larger trade size	Reduces price impact, costs more gas

Picking the right output token

A deep WETH/USDC pool will absorb a large trade with little price impact, while a thin pool against an obscure token can move price sharply on the same size order, so checking pool depth before you swap WETH into a less common asset is worth the extra minute.

WETH follows the ERC-20 approval pattern, so before a router contract can move it on your behalf you sign an approval transaction that authorizes a specific spending allowance. This is separate from the swap transaction itself and only needs to happen once per router, after which every future swap of that token through the same contract skips straight to execution.

Limited versus unlimited allowance

You can approve the exact amount you intend to swap or grant a larger standing allowance for convenience on repeat trades. A tighter allowance means less exposure if that router contract is ever compromised, at the cost of signing a fresh approval more often.

Checking an existing allowance

If a swap fails with an allowance error, the previous approval was either too small or has been revoked; most wallet interfaces surface the current allowance before you sign, so you can confirm it covers the trade you are about to make.

Slippage tolerance sets how far the final price can drift from the quote between the moment you sign and the moment the transaction lands on-chain, while price impact is the cost your own trade size adds by moving the pool's reserves. A tight tolerance protects you from an unfavorable fill but risks the transaction failing if the market moves; a wide tolerance all but guarantees execution but can let a worse price through. For routine trades in a deep WETH pair, a small tolerance is usually enough; for a large size or a thin pool, raising it slightly can be the difference between a confirmed swap and a reverted one.

Reading the minimum received figure

Before you confirm, the interface shows a minimum amount you will receive if price moves against you by the full slippage tolerance. That figure, not the headline quote, is the number worth checking against your own expectations.

The sequence below covers a standard trade from WETH into another token on a decentralized exchange.

• Connect your wallet and select WETH as the token you are swapping from.
• Choose the output token and review the quoted exchange rate and pool fee.
• Approve WETH for the router contract if this is your first swap through it.
• Set a slippage tolerance appropriate to the pool's depth and your trade size.
• Confirm the swap transaction and pay network gas to execute it.
• Verify the received amount in your wallet against the minimum you accepted.

A router does not simply send your trade to one pool; it compares prices across many pools and fee tiers and, for larger orders, splits the trade or chains it through an intermediate token to land on a better overall rate. This matters most when you Swap WETH into a token that does not have a deep direct pool against it, where a single-pool trade can carry far more price impact than a routed path through a more liquid pair. Aggregating liquidity this way is standard practice across major exchanges, documented in the Uniswap docs, and it is also why two interfaces quoting the same pair can show slightly different prices for the same trade.

Comparing routes across exchanges

Decentralized exchanges share the same underlying mechanics described on Wikipedia's overview of the model, but liquidity is fragmented across many of them, so checking an aggregator's quote or a liquidity tracker such as DefiLlama before a large trade can reveal a better route than the first one shown.