Whoever orders a block's transactions can profit from the order

Inherited archive entry · retained from the earlier edition. Its factual, legal and policy claims have not all been reverified for 19 September 2026. Research scope.

Ordering power is worth money

A validator does not just include transactions in a block; within a slot, it chooses their order. Ethereum's documentation defines maximal extractable value as 'the maximum value that can be extracted from block production in excess of the standard block reward and gas fees by including, excluding, and changing the order of transactions'. That definition is deliberately broad: it covers a validator acting alone and a third party paying a validator to act on its behalf. Either way, the source of the value is the same, knowledge of pending transactions combined with the power to sequence them.

What it looks like from inside a trade

The clearest example is a sandwich: a searcher spots a large pending trade, buys the same asset immediately before it to push the price up, lets the large trade execute at the worse price, then sells immediately after. The documentation describes the searcher's software as running 'complex algorithms' to detect such opportunities and submit the surrounding transactions automatically. Arbitrage between two markets showing different prices for the same asset is a less adversarial but related case: a searcher captures the gap, one a slower or less-informed trader would otherwise have captured, or would have caused to persist. In both cases, the person whose transaction was sandwiched or whose arbitrage was pre-empted experiences the cost as ordinary slippage, an unremarkable, unexplained worse price, not a visible attack.

What proposer-builder separation changes and does not

Proposer-builder separation splits the role of assembling a block's contents from the role of proposing it: specialised builders compete to construct the most valuable block and bid for a validator to accept it, rather than every validator running its own ordering logic. Ethereum's documentation describes this as reducing MEV's effect on consensus 'by removing MEV extraction from the purview of validators'. Flashbots' own framing of its purpose is not to eliminate MEV but to 'illuminate' it, 'democratize' access to capturing it, and 'distribute' what remains, an explicit acknowledgement that the value is not removed from the system, only made more visible and less exclusive to whoever happens to run a validator. A user's realised price still depends on the ordering a builder chose; the separation changes who competes for that power and how transparently, not whether ordering power exists.

Questions to carry forward

• Does a given wallet or exchange route trades through infrastructure that reduces sandwich exposure, and how is that verified rather than claimed?
• Who operates the builders and relays a chain's validators rely on, and what happens if a small number of them dominate block construction?
• Is a reported MEV-protection feature preventing extraction, or redistributing the captured value to the user instead of a third party?

MEV is a structural feature of any system where one party orders transactions before they are final, not a bug specific to one chain or tool. The practical question for a user is not whether it exists but which visible or invisible hand is currently doing the ordering, and on whose behalf.