What Happens When You Raise Swap Slippage?

Raising a swap’s slippage tolerance lets it execute after a larger price move, while accepting a worse minimum rate. The setting is a transaction limit: it does not improve the quoted price or reduce the pool’s price impact.

What does the tolerance change in the transaction?

For an exact-input swap, the router receives your fixed input amount and enforces a minimum output, usually called amountOutMin. If the quote is 0.5 ETH for 1,000 USDC and tolerance is 0.5%, the minimum is 0.4975 ETH: the quote multiplied by (1 − 0.005). The trade reverts if execution would return less.

For exact output, you specify the amount you want to receive and the router enforces a maximum input, amountInMax. A quote of 1,000 USDC at 0.5% tolerance permits up to 1,005 USDC. These bounds are encoded in the call; the interface’s estimate can change before the transaction is included.

Uniswap’s V2 pricing reference explains why a pool’s reserves and constant-product curve determine the execution price. A large trade moves along that curve, so price impact is already present in the quote. Slippage tolerance instead covers movement between quoting and execution, including intervening trades, reserve changes, and fees reflected in the route.

How should you choose a value and respond to a revert?

Set tolerance just high enough to cover ordinary movement during confirmation. Around 0.1–0.5% is a common starting range for deep, liquid pairs; volatile or thin pools may need more, but that is a cost decision, not a fix for a poor route. Check the quoted output and price impact first. If the quote is already unattractive, raising tolerance only authorizes a worse fill.

Before: a 1,000 USDC swap quotes 0.5 ETH with 0.5% tolerance, so the lower bound is 0.4975 ETH. After a price move, the route can still execute at 0.498 ETH; if it would return 0.496 ETH, the call reverts. The revert protects the bound, though you may still pay network fees for the failed transaction.

A tight bound can cause repeated failures when the pool is moving or the transaction waits in a congested block. A very loose bound gives searchers more room to sandwich the trade: trade ahead to worsen your execution, then trade back after yours. Raising tolerance does not guarantee a sandwich, but it raises the maximum loss the transaction permits. Check whether the wallet supports a private transaction path before increasing the bound solely to avoid reverts.

Does a higher tolerance guarantee the quoted amount?

No. It sets the worst output you will accept for exact input, or the most input you will spend for exact output. Your execution may be better than that limit, but it can be worse than the current quote. The pool state at inclusion and route fees determine the actual fill.

When should you change the setting instead of retrying?

Change it only if the quote remains acceptable and ordinary price movement is causing the revert. For a QuickSwap trade, compare the route’s quote and impact before adjusting tolerance; the QuickSwap token swap is a concrete case where the minimum-output bound determines whether a changing pool price allows execution. If a small increase still fails, wait for the market to settle or reduce trade size.