What is slippage?

Slippage is the gap between the price you were quoted and the price your swap actually executes at. Blockchains do not settle instantly: between the moment you see a quote and the moment your transaction is mined, other people trade, prices move, and the pool you are buying from shifts. The fill you receive can therefore be a little better or a little worse than expected.

To stop that gap from becoming unbounded, swaps include a slippage tolerance — the maximum adverse move you are willing to accept. If the executed price would fall outside that limit, the transaction reverts instead of filling, and you only pay gas. Set it too tight and ordinary volatility makes trades fail; set it too loose and you expose yourself to bad fills and to sandwich attacks, where a bot deliberately moves the price around your order.

Choosing a sensible tolerance is a balance that depends on the token's volatility and the pool's depth. Stable, liquid pairs can use very low tolerances; thin or fast-moving tokens need more room. Sally lets you control slippage on swaps across Base and BNB Smart Chain and shows the expected price alongside the route, so the protection you set reflects the real conditions of the trade rather than a blind default.