You went to buy a token. The screen showed a price of $0.50. You hit confirm. The transaction completed at $0.515. You paid 3% more than expected.

That's slippage. It's not a bug. It's not your wallet being shady. It's a real feature of how markets work, and especially of how decentralized exchanges work. Once you understand it, you stop getting surprised by it.

What slippage is

Slippage is the difference between the price you saw when you started a trade and the price you actually got when the trade settled. The difference can go in either direction — sometimes you get a better price than expected, more often a slightly worse one.

The bigger the trade and the thinner the market, the more slippage you'll see. A $50 swap on a deep, busy pool might have 0.01% slippage. A $50,000 swap on the same pool might have 2% slippage. A $50,000 swap on a thin pool of a tiny altcoin might have 20% slippage or worse.

Why it happens

Two reasons, depending on the venue.

On centralized exchanges (Coinbase, Binance, Kraken): the order book has bids and asks at specific prices, and a large order eats through the book level by level. Your first 100 tokens fill at the best price. The next 100 fill at a slightly worse price. The cumulative average is your fill price.

On decentralized exchanges (Uniswap, Jupiter, etc.): the math is the seesaw model — as you take from one side of the pool, the other side rebalances and the next unit gets more expensive. The bigger your trade relative to the pool, the more dramatic the rebalance.

Slippage tolerance

Most DEX interfaces have a setting called slippage tolerance. Default is usually 0.5% or 1%. This sets the maximum amount the price can move during your transaction before the transaction fails.

If you set it tight (say 0.1%) and the market moves while your transaction is pending, the transaction will revert — you get your tokens back, but you also pay the gas fee for the failed attempt.

If you set it loose (say 5%), your transaction will go through even if the price moves substantially against you. This is dangerous on illiquid tokens because of MEV.

MEV — the slippage you didn't ask for

There's a darker version of slippage that happens specifically on Ethereum and similar chains: maximum extractable value, usually shortened to MEV.

The mechanism: when you submit a swap to a DEX, your transaction sits in a public queue (the mempool) for a few seconds before being included in a block. Bots watch this queue. When they see a swap with loose slippage tolerance on an illiquid pool, they execute their own transaction immediately before yours (buying the token to push the price up), let yours execute (at the new, higher price), and then sell. The bot pockets the difference. You ate the slippage.

This is called sandwich attacks. It's automated, common on Ethereum mainnet, and it specifically targets traders with loose slippage settings.

How to keep slippage from costing you

A few practical defenses:

  1. Use realistic slippage settings. 0.5% to 1% is appropriate for major tokens on deep pools. For smaller tokens, you may need more, but be conservative.
  2. Trade on aggregators. Jupiter (Solana), 1inch and CowSwap (Ethereum/EVM) split your trade across multiple pools to minimize slippage. Their quoted prices include fees and slippage.
  3. For larger trades, break them up. Three $10,000 trades over a few hours usually beat one $30,000 trade.
  4. Use limit orders when you can. Some DEXs and aggregators now support real limit orders. You set the price; the order executes only if the market reaches it. No slippage.
  5. Avoid trading the moment a token launches. The first hour of a new token's life has terrible slippage, brutal MEV bots, and frequent rug pulls. The "early bird" cost almost always exceeds the gain.

Slippage on centralized exchanges

This is less of a problem on big exchanges with deep order books. A small or medium retail trade on a major asset on Coinbase or Binance has very little slippage — you're effectively at the spread. It mostly becomes an issue with very large orders or on thinly traded altcoins.

Takeaway

Slippage is normal. It exists on every exchange. The amount you pay in slippage is a function of your trade size, the depth of the market, and your slippage tolerance setting. For most retail trades on major assets, it's a rounding error. For larger trades on thinner markets, it's worth paying attention to and worth using tools designed to minimize it.

If a swap quote feels off, check the slippage estimate before confirming. It's almost always shown right there.