What is slippage?

Slippage occurs when an order consumes more than the quantity available at the best price and fills progressively deeper into the order book.

Why it matters

On a liquid pair and a small order it is negligible. On a thin pair, a large order, or during volatility it can dwarf the trading fee you were carefully comparing. This is the cost most fee comparisons ignore entirely, because it does not appear as a line item — it is simply a worse price. Slippage is why the quoted rate on any converter, including ours, is a reference figure rather than a quote, and why splitting a large order or using limit orders matters more than shaving a basis point off a fee.