What is Slippage?
How it works
AMM pools reprice with every swap. In a constant-product pool (x*y=k), buying token X removes it from the pool and pushes its price up along the curve — so the larger your trade relative to pool depth, the worse your average execution price. This portion, called price impact, is deterministic and quoted before you sign: a $100k swap barely moves a $500M pool but devastates a $1M one. Curve-style stable pools flatten the curve for like-priced assets specifically to minimize this.
The second source is execution delay. Between signing a transaction and its inclusion in a block, other swaps can shift the pool's price. To bound the damage, routers let you set a slippage tolerance, encoded on-chain as a minimum-output amount. If execution would return less than that minimum, the swap reverts — you keep your tokens but still pay gas.
Tolerance is a trade-off. Set it too tight and volatile markets revert your trades repeatedly; set it too loose and you invite sandwich attacks: MEV bots spot your pending swap, front-run it to push the price up to your limit, let you fill at the worst allowed price, then sell back for profit. Aggregators like 1inch split orders across pools, and batch-auction venues like CoW Swap settle off the public mempool, both reducing what searchers can extract.
Why it matters
Slippage is a real trading cost that never shows up as a line-item fee, and it scales brutally with trade size and thinning liquidity — long-tail tokens and stressed markets are where it bites hardest. It is also the attack surface for the most common form of MEV: sandwich bots have cumulatively extracted hundreds of millions of dollars from traders whose slippage tolerances were set too loose. Understanding the difference between price impact (your trade's own footprint) and slippage tolerance (your on-chain safety rail) is the difference between paying a few basis points and donating your trade to a bot.
Real-world examples
On 11 March 2023, during the USDC depeg panic, a trader dumped roughly $2.08 million of 3CRV (Curve's stablecoin LP token) into a thin Uniswap v2 pool with slippage protection effectively disabled. An MEV bot sandwiched the transaction — front-running to drain the pool, letting the swap fill at a catastrophic price, then back-running for the profit. The trader received about $0.05 of USDT; the bot cleared roughly $2 million, paying most of it to the block producer to guarantee ordering. Near-total loss, purely from unbounded slippage.
FAQ
What slippage tolerance should I set?
For deep, liquid pairs like ETH/USDC, 0.1–0.5% is typical. Volatile or thin long-tail tokens may need 1–3% to avoid reverts — but every extra point of tolerance is profit you are offering to sandwich bots. Rather than cranking tolerance up, use an aggregator with MEV protection or a private RPC that keeps your transaction out of the public mempool.
Is slippage the same as price impact?
No. Price impact is the deterministic price move your own trade causes against current pool liquidity, and it is quoted before you sign. Slippage is the total difference between quoted and executed price, which also includes other transactions landing first. Trading interfaces often blur the two, but only the second part is unpredictable.
Can slippage be positive?
Yes. If the price moves in your favor between submission and execution, you receive more than quoted. Some venues, notably CoW Swap's batch auctions, return this surplus to the trader; on traditional AMM routers, favorable movement is simply reflected in your output — though in practice MEV searchers capture most exploitable price gaps first.
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