Slippage is the gap between the price you expect and the price you actually get. It shows up on market orders, large tickets, and fast markets when the book cannot absorb your size at the quoted level. Limits and smaller clips reduce it. Ignoring depth invites paying for speed with worse fills, which can erase the edge you thought the chart was offering.
Why it matters
Slippage turns a good mid-price idea into a bad average entry. Strategies that look fine on a candle chart can fail after costs when every entry walks the book. That is why desks check liquidity before sizing, especially on alts, new pairs, and during news bursts when quoted sizes disappear in seconds.
On-chain swaps add another layer. Pool depth, price impact curves, and gas timing all affect the final rate. A quoted mid can expire before the transaction lands, and failed attempts can still burn gas fees. Setting a max slippage tolerance protects you from extreme fills, but a tight tolerance can also cause failed transactions when volatility spikes.
Slippage is not always a bug in the venue. Sometimes it is the honest price of demanding immediacy in a thin market. The calm response is to change order type, split size, wait for thicker hours, or skip the trade. Chasing a fill that already moved against you often compounds the mistake and turns one bad clip into a full-size regret.
Example
The screen shows 10,000 dollars of bids near your target. You market-sell 50,000 dollars into that book and average far below the last print. Splitting the order, using a limit near the mid, or cutting size to match visible depth would have been the mechanical fix. The lesson is clear: expected price assumed depth you did not have.