What is MEV (maximal extractable value)?

MEV, short for maximal extractable value (originally “miner extractable value”), is the profit that can be captured by whoever decides the order, inclusion, or exclusion of transactions in a block. Because block producers on public blockchains choose how pending transactions are arranged, that ordering power has monetary value — and MEV is the name for the value extractable from exercising it.

This article explains where MEV comes from, the main forms it takes, and how the ecosystem tries to manage it. It is educational and describes mechanics at an awareness level; it is not a guide to extracting MEV.

Where MEV comes from

On a public blockchain, transactions do not settle the instant they are sent. They wait in a public holding area — the mempool — where anyone can see them before they are confirmed. A block producer (a validator on a proof-of-stake network) then selects transactions from this pool and decides the exact order in which they will be recorded.

That ordering is not neutral, because the outcome of many transactions depends on what happens immediately before them. A large trade on a decentralised exchange, for instance, will move the price for the next transaction. Whoever controls ordering can position transactions around others to capture value that arises purely from sequence. This ability to reorder, insert, or omit transactions is the raw material of maximal extractable value.

The main forms of MEV

MEV is not a single activity but a family of them. The most discussed forms include:

• Arbitrage. When the same asset trades at different prices across venues — for example two automated market makers — a transaction can buy on the cheaper one and sell on the dearer one in the same block. This is widely considered benign or even helpful, because it brings prices into line. See arbitrage.
• Liquidations. Lending protocols allow undercollateralised positions to be liquidated for a reward. Competing to be the transaction that performs a valid liquidation is a common source of MEV.
• Sandwich activity. A pending trade visible in the mempool can be surrounded by two transactions — one placed just before it and one just after — profiting from the price impact the victim’s own trade creates. This form is extractive: it makes the sandwiched user’s execution worse. We describe it at an awareness level so readers understand the risk, not as a method to reproduce.

The first two are broadly seen as part of healthy market function; the third is the kind of MEV that harms ordinary users and drives much of the effort to contain it.

Why MEV matters to ordinary users

Even if you never seek MEV, it affects you. When a transaction sits in the public mempool, its intended outcome can be degraded by others positioning around it, which shows up as worse execution than expected — a practical form of slippage. Competition to capture MEV can also congest the network and raise fees, as searchers bid up gas to have their transactions ordered favourably. In short, MEV is a hidden cost embedded in how public blockchains process transactions, and it is one reason execution on-chain can differ from a naive expectation.

The MEV supply chain

Over time, an entire pipeline has grown up around MEV, partly to make it more orderly and less damaging. The roles are usually described as:

• Searchers — participants who scan pending transactions and on-chain state for profitable opportunities and construct bundles of transactions to capture them.
• Builders — specialists who assemble complete, ordered blocks from many submitted bundles and ordinary transactions, competing to produce the most valuable block.
• Proposers (validators) — the block producers who ultimately publish a block, often selecting the most valuable one offered to them.

Separating these roles is the idea behind proposer-builder separation, an approach promoted on Ethereum to reduce the advantage that would otherwise accrue to the largest validators and to make MEV extraction more transparent. Projects such as Flashbots publish research and tooling in this area, and Ethereum’s own documentation explains the concepts in detail.

A concrete example: cross-venue arbitrage

To make MEV tangible, consider a benign arbitrage case, described purely to illustrate the mechanism. Suppose the same token trades slightly cheaper on one automated market maker than on another at the same instant. A searcher spots this in the pending state and constructs a bundle: within a single block, buy the token where it is cheaper and sell it where it is dearer, pocketing the difference.

Two features make this MEV rather than ordinary trading. First, it depends on ordering — the two legs must execute in the right sequence within the same block to lock in the gap. Second, searchers compete for it, often bidding higher fees so their bundle is included over rivals. The economic side effect is usually seen as positive: the arbitrage nudges the two venues back toward the same price. It is the clearest case of MEV that helps rather than harms.

Reorgs and why finality matters

In its more extreme theoretical forms, the value of controlling ordering can create an incentive to reorganise recently produced blocks — a “reorg” — to capture MEV that was awarded to someone else. This is a serious concern because it threatens the stability of the chain itself, not just individual users. Networks and researchers treat resistance to such reorg incentives as a core design goal, which is one reason strong, fast finality and the structural reforms described below are considered important. For most readers the takeaway is simply that MEV is not only a per-transaction cost but also something protocol designers weigh at the level of chain security.

How the ecosystem tries to manage MEV

Because MEV cannot simply be abolished — it is a consequence of transparent, ordered blocks — the focus is on managing and redistributing it. Approaches under active development include:

• Private transaction routing. Sending transactions through channels that do not expose them in the public mempool, reducing the chance of being sandwiched.
• Proposer-builder separation. Structurally splitting who builds a block from who proposes it, to limit centralising incentives.
• Fairer ordering research. Protocol-level ideas aimed at making transaction ordering less exploitable, and at returning some extracted value to users.

These are evolving areas rather than settled solutions, and their effectiveness is still debated. The relevant point for a general reader is that MEV is a known structural feature being actively worked on, not a bug that has been fixed.

Which blockchains have MEV

MEV is not unique to one network; it is a general consequence of a design where transactions are publicly visible before confirmation and a producer decides their order. Any blockchain with those properties has some form of MEV, though its scale and character vary. Networks with rich decentralised-finance activity — many trading venues, lending protocols, and liquidations happening on-chain — tend to have more MEV opportunities, simply because there are more transactions whose outcome depends on ordering. Design choices also matter: a chain with a private or encrypted transaction pool exposes less to would-be extractors than one with a fully public mempool, and different consensus and block-production models distribute the opportunity differently. The general point is that MEV is a structural feature of transparent, ordered ledgers rather than a flaw in any single project, which is why it is studied as a cross-chain phenomenon rather than a one-network bug.

The bottom line

MEV — maximal extractable value — is the value that flows from controlling how transactions are ordered, included, or excluded in a block. Some of it, like arbitrage and liquidations, helps markets function; some of it, like sandwich activity, extracts value from ordinary users at their expense. A whole supply chain of searchers, builders and proposers now exists around it, and mechanisms such as private routing and proposer-builder separation aim to make it less harmful. Understanding MEV explains why on-chain execution can quietly cost more than the visible fee suggests.