Slippage is the difference between the price displayed when you initiate a trade and the price at which it actually executes. On a DEX, it happens because executing your trade changes the pool’s token ratio, which moves the price. On a centralized exchange, it happens when the order book lacks enough depth at your target price and fills at progressively worse prices further into the book.
How slippage works on DEXes
On a DEX using a constant product AMM, your trade moves the pool ratio toward the token you are buying. The bigger your trade relative to the pool’s total liquidity, the more the ratio shifts during execution and the worse your average fill price. This is called price impact. Slippage tolerance is the maximum price impact you are willing to accept; if the actual price impact at execution exceeds this tolerance, the transaction reverts rather than fill at the worse price.
Setting a tight slippage tolerance (0.1%) reduces the chance of a bad fill but increases the chance of a failed transaction in volatile markets. Setting a wide tolerance (1 to 3%) ensures the transaction executes but gives MEV bots a larger sandwich window. See: MEV explained and AMM pricing explained.
What this means for traders
For liquid pairs (ETH/USDC, BTC/USDC) on deep DEX pools, a $10,000 swap has price impact below 0.1% and slippage is negligible. For new tokens with shallow liquidity, a $1,000 swap can cause 5 to 10% price impact. The DEX interface shows price impact before you confirm; anything above 1% on a mainstream asset is a warning sign that the pool is too thin for your trade size.
Use an aggregator (1inch, Paraswap) to split large orders across multiple pools and minimize total price impact. For tokens with very thin liquidity, consider using a limit order rather than a market swap. See: liquidity pools explained.
A concrete example
You swap $20,000 USDC for ETH on Uniswap. Pool has $500,000 in liquidity. Price impact: roughly 2%. You receive ETH worth $19,600 at the pre-swap quoted price. Same swap on a pool with $5 million in liquidity: price impact roughly 0.2%, you receive $19,960. Routing the same $20,000 through 1inch, which splits it across three pools, reduces average price impact to 0.15%, giving you $19,970. The only variable that changes your outcome is pool depth and routing; the token and protocol stay the same.
Frequently asked questions
Does slippage tolerance prevent front-running?
No. A tight slippage tolerance limits how bad your fill can be, but MEV bots can still sandwich your trade within your tolerance window. To prevent front-running, use a private RPC endpoint like MEV Blocker or route through 1inch Fusion rather than relying on slippage tolerance alone.
Is slippage the same as swap fees?
No. Swap fees (0.3% on Uniswap v2, variable on v3) are a fixed cost paid to liquidity providers. Slippage is the additional cost from your trade moving the pool price. A $1,000 swap on a $100,000 pool might cost 0.3% in fees plus 0.5% in price impact slippage. They are separate costs that both reduce your effective fill price.
How do limit orders avoid slippage?
DEX limit orders, available on protocols like CoW Swap, 1inch, and Uniswap v4, execute only when the market reaches your specified price. You accept the possibility of no fill in exchange for price certainty. For large trades on illiquid tokens, limit orders eliminate slippage risk entirely at the cost of execution uncertainty.
