Slippage, sandwiches, and MEV: the hidden taxes on every swap

A DEX swap rarely executes at the on-screen price. The difference is not mysticism but three specific mechanisms.

The three levies

• Slippage: your own swap moves the pool's price (see the AMM mechanics). The slippage tolerance setting is your pain limit: too low - the transaction fails, too high - an invitation for...
• The sandwich attack: a bot sees your swap in the mempool, buys ahead of you (pushing the price up), lets you execute at the worse price, and sells right after. Your inflated slippage is its profit. This is the most widespread form of MEV.
• The route toll: pool and aggregator fees. A crooked route through three pools collects the fee three times.

How to pay less

• Private transactions: sending around the public mempool (protected RPCs) - the sandwich bot cannot see you.
• Aggregators with MEV protection and smart routing: they compare routes and hide the order.
• Slippage sized to the trade: minimal for liquid pairs; for exotics - split the order into parts.
• Limit orders on DEXes that have them - no slippage at all.

On small amounts these are cents; on serious volume the MEV tax runs to percents. The protection infrastructure is mature - not using it in 2026 is simply laziness.