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What Is Slippage, and How Should You Set Slippage Tolerance?

Slippage is the gap between the quoted price and the price your swap actually executes at. Learn why AMMs cause it, the trade-offs of slippage tolerance, and why extreme slippage demands are a red flag.

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BlockVar Editors
· 19 min read
What Is Slippage, and How Should You Set Slippage Tolerance?

The first time you swap tokens on a decentralized exchange, you will probably notice a setting called slippage. Some beginners never touch it and watch their transactions fail again and again. Others hear that "just crank the slippage up and it will go through" — and end up with a much worse price than expected, or squeezed by a hostile bot in the middle of their trade.

Slippage is the difference between the price you are quoted when you submit a swap and the price at which the trade actually executes on-chain. The interface may show that 1 ETH gets you 3,000 units of a token, but by the time your transaction is included in a block, you might receive 2,980. That 0.67% gap is slippage.

Slippage itself is not a scam. It is a natural consequence of how on-chain trading works. What matters is understanding why it happens, what the slippage tolerance setting actually protects, and when "abnormal slippage" is a warning sign rather than a nuisance.

Why slippage exists at all

Most decentralized exchanges use an AMM (automated market maker). Prices are not set by an order book; they come from the ratio of two assets in a liquidity pool. Every unit you buy shifts that ratio, which pushes the price against you. In other words, your own trade moves the price — and the larger the trade or the smaller the pool, the bigger the move.

There is also a timing gap. Between the moment you click confirm and the moment your transaction lands in a block, seconds may pass — and other people's trades keep changing the pool in the meantime. The quote you saw was a snapshot; the world has moved on by the time you execute.

So slippage is nearly unavoidable on an active chain. Small trades in deep pools of mainstream tokens usually see tiny slippage. Large trades in shallow pools of obscure tokens can see slippage that is genuinely painful.

What slippage tolerance actually protects

Slippage tolerance is the floor you set for your trade: if the execution price is worse than the quote by more than this percentage, the transaction fails and reverts instead of filling at the worse price.

Two things worth internalizing:

  • It is a maximum acceptable gap, not a guaranteed loss. Setting 1% does not mean you lose 1%; most of the time actual slippage is far below your tolerance.
  • When a trade reverts, your tokens are not swapped, but the gas already spent is generally not refunded.

What happens when it is too low — or too high

Too low: in volatile conditions or shallow pools, the real price easily drifts outside your tolerance, so trades fail repeatedly. Each failure still burns gas.

Too high: you are effectively announcing that you will accept a much worse price. Two problems follow. First, in a fast market you really will get filled at that worse price. Second, you become a target for MEV sandwich attacks: a bot sees your pending transaction in the mempool, buys just before you to push the price up, lets you fill at the inflated price, then sells immediately for a profit. The higher your tolerance, the more room the bot has to extract.

As a rough reference: for mainstream pairs like ETH/USDC in deep pools, 0.1%–0.5% is usually enough; volatile or moderately liquid tokens may need around 1%. If a token only trades when you set slippage to 5%, 10%, or more — stop and ask why before going further.

Abnormal slippage is a red flag

Sometimes "you must set very high slippage" is itself the alarm:

  • Transfer taxes: some tokens automatically deduct a percentage on every buy or sell, which shows up as a fixed chunk of extra slippage. Check whether the tax is disclosed and reasonable before buying.
  • Honeypot tokens: these can be bought but not sold, or charge an extreme tax on selling. People who discover they "can't sell" often raise slippage to 50% or 90% in desperation — which just hands the tokens over. If a token only sells at extreme slippage, it is very likely a honeypot, and raising slippage further only increases the loss.
  • Extremely shallow liquidity: with very little in the pool, any normal-sized trade causes a huge price impact. Even if such a token is not an outright scam, getting in and out is very expensive.

For any unfamiliar token, test with a tiny amount first — one small buy and one small sell — to confirm it trades in both directions before doing anything larger.

A pre-swap slippage checklist

  • Confirm the trading interface comes from the official entry point, not a lookalike site.
  • Check the estimated price impact of the trade; if it exceeds 1%–2%, consider a smaller size.
  • Work upward, not downward: start with the default or 0.5%, and only raise tolerance in small steps after a failure.
  • Test unfamiliar tokens with a small buy and sell to rule out honeypots.
  • For large trades, consider splitting into several smaller ones, or routing through deeper pools or an aggregator.
  • Check the "minimum received" figure in the wallet popup and make sure you can live with it.
  • When a trade fails, read the failure reason first — do not reflexively crank up slippage.

FAQ

If I set 1% slippage, will I always lose 1%? No. Tolerance is a ceiling. Most trades execute with far less actual slippage. The setting exists so that anything beyond the ceiling fails automatically instead of filling at a bad price.

My swap keeps failing with a slippage error. Should I just raise it? Diagnose first. If it is a mainstream token in a volatile moment, a small increase is fine. If an unfamiliar token demands extreme slippage to trade, it likely has a transfer tax or is a honeypot — do not keep raising it.

What is a sandwich attack? An MEV bot places one transaction just before yours and one just after: it buys to push the price up, lets you fill at the inflated price, then sells for profit. High slippage tolerance gives the bot more room. Some wallets and RPC services offer private transaction routing to mitigate this.

Are slippage and gas fees the same thing? No. Gas is the execution fee paid to the network and is usually consumed whether or not the swap succeeds. Slippage is the gap between quoted and executed price. When slippage protection reverts a trade, the gas is generally not refunded.

References

FAQ slippageslippage toleranceAMMsandwich attackMEVhoneypot token

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