In one sentence
The difference between the price you expected when placing an order and the actual price at which it executed, which grows when liquidity is scarce, volatility is high, or the order is too large for the market.
Slippage is the difference between the price you expected when you placed an order and the actual price at which it executed. It almost always works against you, and it grows when liquidity is scarce, volatility is high, or your order is too large for the market.
Milliseconds pass between the moment you tap “buy” and the moment the market executes your order. In a liquid, calm market, the price hasn’t moved: you pay what you saw. In an agitated or shallow one, the price you saw no longer exists: you pay whatever is there. That difference, multiplied across thousands of trades, is one of the most overlooked profitability leaks for new traders, who scrutinize fees under a magnifying glass while slippage charges them double through the back door.
Why slippage happens: the order book has gaps
On an exchange, buy and sell orders stack up at different prices in the order book. A market order keeps consuming the best prices available: if you buy a small amount, the first price tier covers it; if you buy a lot, you keep “eating” progressively worse tiers, and your average price drifts away from what you saw on screen. Three factors make it worse: low liquidity (empty tiers), high volatility (the tiers move while you’re executing), and an order size that’s disproportionate to the market.
Slippage in numbers: the invisible cost
You want to buy $50,000 pesos’ worth of a small token trading at 1.00. The order book has little depth: your market order fills in tranches at 1.01, 1.03, and 1.06. Final average price: 1.033. You paid 3.3% more than what you saw on screen, about 1,650 pesos that show up on no fee receipt anywhere. In Bitcoin or Ethereum, that same trade would have had slippage of a few hundredths of a percent: liquidity is the difference.
Slippage is amplified in DeFi
On a DEX you’re not trading against an order book but against a liquidity pool, and the pool’s formula raises the price as your own order consumes it: slippage is guaranteed by design, and only its size varies. That’s why DEX interfaces include a “slippage tolerance” control: the maximum deviation you’ll accept before the transaction cancels itself.
Setting it has its trap. Tolerance too low: transactions fail on-chain (and you pay the gas anyway). Tolerance too high: you become prey for MEV bots, which spot your pending transaction in the mempool, buy ahead of you, sell to you at a higher price within your tolerated margin, and pocket the difference (the infamous sandwich attack). The setting is a risk dial, not a formality.
How to reduce slippage, in order of effectiveness
Trade liquid assets, which is the biggest and simplest lever. Use limit orders when the exact price matters: they eliminate negative slippage by definition (in exchange for the risk of not executing). Split large orders into tranches. Avoid trading during spikes of panic or euphoria, when order books empty out. And on DEXs, use low tolerance (0.1-0.5% on stable pairs), networks with more liquidity, and aggregators that split your order across several pools to minimize impact.
Measuring slippage before you trade
Slippage can be estimated before you suffer it. On an exchange, the order book depth view shows how much volume is waiting at each level: if your order exceeds what’s stacked in the first tiers, you already know you’re going to slip. On DEXs, the interfaces calculate and display the “price impact” before you sign: an impact of 0.1% is routine; one of 5% is the market warning you that you’re too big for that pool. The operating rule is that if your trade visibly moves the price, you don’t have an order, you have an event; split it or find a deeper market.
