When you swap, your trade moves a pool's price away from every other pool trading the same pair. Somebody trades it back and keeps the difference. On BNB Chain in 2026, that somebody is usually the company that built the block.
Two kinds of MEV, and which one still happens
A sandwich trades in front of you and behind you: a bot buys first so you pay more, then sells into the price you pushed up. It needs to see your transaction while it is still pending in the public mempool.
A backrun trades only behind you. It cannot change the price you got, because your swap has already executed when it runs; it closes the gap your swap opened between pools and keeps that gap as profit.
What we measured
We read every block from our own full node in Tokyo and classify each transaction from its receipts, reading native BNB movements from call traces where the logs cannot show them.
- Sandwiches: essentially none against users. Over about 20 hours of blocks (roughly 164,000) on PancakeSwap V2 and V3, Uniswap V3 and V4 and PancakeSwap Infinity pools, the only sandwich-shaped patterns were volume-farming wallets trading with each other for cents. BNB Chain's block builders refuse sandwich bundles, and it shows.
- Backruns: almost every swap. In the first twenty minutes of the live measurement, 3,318 swaps from 973 wallets leaked about $2,283 to the arbitrage placed right behind them.
- Who took it: the builders. 97 % of that went to the builders' own arbitrage contracts — about $1,474 to 48Club's and $740 to BlockRazor's — inside the blocks they built. Independent searchers shared the remaining few percent.
Most leaks are cents. The large ones come from big trades in thin pools: one sale of 33 million tokens for 4.08 WBNB leaked 0.415 WBNB, about a tenth of the trade's value, to a single backrun in the same block.
The live numbers, and a lookup for your own wallet, are on the leak check.
What you can do about it
- Trade size against pool depth matters most. A leak is a slice of your price impact. Splitting a large trade, or routing it through deeper pools, leaves less gap behind it.
- Slippage limits do not stop backruns. They protect you from a worse fill, which is what a sandwich would cause; a backrun happens after your fill and does not change it.
- A private RPC keeps your pending transaction out of the public mempool. On BNB Chain today that mainly protects you from the rare sandwich and from being traded against before you land.
- A rebate RPC can return part of the backrun to you — but only for backruns it actually captures. Because the builders' own contracts take most of this value inside their own blocks, no outside rebate can return all of it. Be wary of anyone who promises otherwise.
How the numbers are made
An arbitrage is a transaction whose sender ends with more of a token it both paid into a pool and took out of one, and less of none. The swap it leaked from is the nearest earlier swap on one of its pools in the same block. What leaked is that arbitrage's profit, including what it paid on to the builder and validator — a floor on what the swap gave away. A row claiming more than half of the swap's own value is dropped as a measurement error rather than shown. Our node can trace only recent blocks, so the record begins on 23 September 2026.