What is maximum extractable value (MEV)?

Between clicking swap and a trade landing in a block, bots can reorder transactions to profit at the trader's expense. A guide to MEV across blockchains, and how to minimize it.

• MetaMask
• Why MEV exists
• Common types of MEV
• How an MEV sandwich attack works
• MEV across blockchains
• Who captures MEV: searchers, builders, and validators
• Can MEV be fixed?
• Common ways to reduce MEV exposure

Maximal extractable value (MEV) is the profit that can be made by choosing which transactions go into ablockchain block and in what order. It exists on any network where someone decides transaction order, including Ethereum, Solana, BNB Chain, layer 2 networks and, in more limited forms, Bitcoin. Specialized traders called searchers run bots that watch for pending transactions, such as large token swaps, and pay to place their own transactions just before or after them to capture the price difference.

Disclaimer: This guide is for educational purposes only. It is not financial advice, not a solicitation, and not for UK audiences. Trading, swaps, and the networks described here carry risk and are not suitable for all users.

Why MEV exists

On most blockchains, a submitted transaction waits briefly before it's included in a block. On many networks it waits in a public mempool, where anyone can see it. Whoever builds the block decides the order, and they often take payments to put certain transactions first, on top of standardnetwork fees. A swap's price depends on the trades ahead of it, so a swap that executes after a large buy order gets a worse price than one that executes before it.

How block production works depends on the network. On Ethereum, it's split between two parties. First, block builders (specialized operators) collect pending transactions and searchers' bundles and arrange them to earn the most from fees and bundle payments. Then the validator proposing the next block picks the builder whose block pays it the most. Solana has no public mempool. Instead, most validators run Jito's client, which accepts bundles of transactions with tips through a on offchain block engine.

MEV was first called "miner extractable value," because on Ethereum, as on Bitcoin, miners chose transaction order under proof of work. Since Ethereum moved to proof of stake in September 2022, "maximal extractable value" has become the standard term, because validators, block builders, and searchers now share the value.

Common types of MEV

Not all MEV hurts users. Some of it keeps markets working. Sandwich attacks and front-running are the forms that directly cost traders money.

• Arbitrage. A bot spots the same token priced differently on two exchanges and trades to close the gap. This keeps prices aligned across venues.

Arbitrage. A bot spots the same token priced differently on two exchanges and trades to close the gap. This keeps prices aligned across venues.

• Liquidations. When a loan on a lending protocol falls below its collateral requirement, bots compete to repay it and collect a liquidation reward. This keeps lending protocols solvent.

Liquidations. When a loan on a lending protocol falls below its collateral requirement, bots compete to repay it and collect a liquidation reward. This keeps lending protocols solvent.

• Front-running. A bot sees a pending transaction and places a similar one ahead of it with a higher fee, taking the opportunity first.

Front-running. A bot sees a pending transaction and places a similar one ahead of it with a higher fee, taking the opportunity first.

• Sandwich attacks. A bot places one trade before a victim's swap and another right after it, profiting from the price movement the victim's trade causes.

Sandwich attacks. A bot places one trade before a victim's swap and another right after it, profiting from the price movement the victim's trade causes.

• Back-running. A bot places a transaction directly after a large trade to capture an arbitrage it creates. This usually doesn't cost the original trader anything extra.

Back-running. A bot places a transaction directly after a large trade to capture an arbitrage it creates. This usually doesn't cost the original trader anything extra.

How an MEV sandwich attack works

Most sandwich attacks follow the same four-step pattern:

• A traderplaces a swap with slippage tolerance set to 2%. That setting tells the swap to cancel if the price moves more than 2% before it goes through.

A traderplaces a swap with slippage tolerance set to 2%. That setting tells the swap to cancel if the price moves more than 2% before it goes through.

• A bot spots the swap while it's still pending and buys the same token ahead of it, which raises the price.

A bot spots the swap while it's still pending and buys the same token ahead of it, which raises the price.

• The trader's swap goes through at this inflated price, because it's still inside the 2% limit. That purchase raises the price even more.

The trader's swap goes through at this inflated price, because it's still inside the 2% limit. That purchase raises the price even more.

• The bot immediately sells its tokens at the new, higher price and pockets the gap.

The bot immediately sells its tokens at the new, higher price and pockets the gap.

The trader ends up with fewer tokens than the same swap would normally buy. A bot can take no more than the slippage tolerance allows, so large trades with loose slippage settings are the most attractive targets. This can happen on any network where blockchain exchanges exist and transaction order can be influenced.

MEV across blockchains

• Ethereum: The most-studied MEV market, with a formal system for splitting block production between roles (see below).

Ethereum: The most-studied MEV market, with a formal system for splitting block production between roles (see below).

• Solana: Sandwich attacks are common. Most MEV flows through Jito's bundle and tip system rather than a public mempool.

Solana: Sandwich attacks are common. Most MEV flows through Jito's bundle and tip system rather than a public mempool.

• Layer 2 networks: Many order transactions through a single sequencer, often first come, first served, which limits classic sandwiching but can shift MEV toward speed-based competition.

Layer 2 networks: Many order transactions through a single sequencer, often first come, first served, which limits classic sandwiching but can shift MEV toward speed-based competition.

• Bitcoin: MEV is limited, because Bitcoin has few blockchain trading apps. It mostly comes from fee bidding and transaction ordering.

Bitcoin: MEV is limited, because Bitcoin has few blockchain trading apps. It mostly comes from fee bidding and transaction ordering.

Who captures MEV: searchers, builders, and validators

Who captures MEV depends on how a network produces blocks. Ethereum has the most formal setup, where block production is split between roles:

• Searchers run bots that find MEV opportunities and package them as bundles of transactions.

Searchers run bots that find MEV opportunities and package them as bundles of transactions.

• Block builders combine bundles and regular transactions into the most profitable block they can.

Block builders combine bundles and regular transactions into the most profitable block they can.

• Relays pass blocks from builders to validators without letting validators see the contents early.

Relays pass blocks from builders to validators without letting validators see the contents early.

• Validators propose the block that pays them the most.

Validators propose the block that pays them the most.

This system is called proposer-builder separation. It runs mainly through MEV-Boost software, which more than 90% of Ethereum validators use, according to Bitcoin.com News. Block building is concentrated: as of October 28, 2026, relayscan.io showed one block builder, Titan, producing about 53% of MEV-Boost blocks, and three MEV-Boost relays delivering about 83% of them. On other networks, the validator or sequencer that produces the block usually captures MEV directly or through tips.

Can MEV be fixed?

MEV can't be removed entirely, because someone always decides the transaction order. But several approaches target the harmful forms of MEV:

• Enshrined proposer-builder separation (ePBS): Ethereum's next upgrade, Glamsterdam, includes EIP-7732, which writes the builder auction into Ethereum's consensus rules so validators no longer rely on relays. Glamsterdam went live on the Sepolia testnet on October 6, 2026. Its Hoodi testnet launch was postponed on October 23, and no mainnet date has been set as of November 2026.

Enshrined proposer-builder separation (ePBS): Ethereum's next upgrade, Glamsterdam, includes , which writes the builder auction into Ethereum's consensus rules so validators no longer rely on relays. Glamsterdam went live on the Sepolia testnet on October 6, 2026. Its Hoodi testnet launch was postponed on October 23, and no mainnet date has been set as of November 2026.

• Order flow auctions: Private transaction channels let searchers bid only to back-run a transaction, not to front-run it, and return part of the profit to the user who sent it.

Order flow auctions: Private transaction channels let searchers bid only to back-run a transaction, not to front-run it, and return part of the profit to the user who sent it.

• Encrypted mempools: Transactions stay encrypted until their order is fixed, so bots can't read them in advance. Shutter network’s encrypted mempool has run on Gnosis Chain since July 2024. An Ethereum version has been proposed but isn't live as of October 2026.

Encrypted mempools: Transactions stay encrypted until their order is fixed, so bots can't read them in advance. network’s encrypted mempool has run on Gnosis Chain since July 2024. An Ethereum version has been proposed but isn't live as of October 2026.

• Protocol-level protection: Some layer 1 networks, such as Sei, build MEV protection into the blockchain itself.

Protocol-level protection: Some layer 1 networks, such as , build MEV protection into the blockchain itself.

• MEV burn: A research proposal to burn part of Ethereum's MEV rewards instead of paying them to block producers. It isn't scheduled for any Ethereum upgrade.

MEV burn: A research proposal to burn part of Ethereum's MEV rewards instead of paying them to block producers. It isn't scheduled for any Ethereum upgrade.

Common ways to reduce MEV exposure

• Private transaction submission: Sending a transaction through a private channel instead of the public mempool keeps it hidden from bots until it's in a block. Some wallets, like MetaMask, do this by default.MetaMask's MEV protection privately auctions eligible transactions instead of sending them to the public mempool, where front-running and sandwich bots look for targets.

Private transaction submission: Sending a transaction through a private channel instead of the public mempool keeps it hidden from bots until it's in a block. Some wallets, like MetaMask, do this by default.MetaMask's MEV protection privately auctions eligible transactions instead of sending them to the public mempool, where front-running and sandwich bots look for targets.

• Tighter slippage tolerance: A lower slippage tolerance limits how much a sandwich attack can take, though too low a setting can cause swaps to fail.

Tighter slippage tolerance: A lower slippage tolerance limits how much a sandwich attack can take, though too low a setting can cause swaps to fail.

• Splitting large trades: Smaller trades move the price less and offer bots less profit.

Splitting large trades: Smaller trades move the price less and offer bots less profit.

• Batch auctions and intent-based swaps: Some platforms collect orders and settle them together at one price, which removes the ordering advantage. Seebest crypto swap platforms 2026.

Batch auctions and intent-based swaps: Some platforms collect orders and settle them together at one price, which removes the ordering advantage. Seebest crypto swap platforms 2026.

• Choosing the network: Layer 2 networks with a single sequencer, and networks with built-in MEV protection, expose trades to fewer ordering attacks.

Choosing the network: Layer 2 networks with a single sequencer, and networks with built-in MEV protection, expose trades to fewer ordering attacks.

Frequently asked questions about MEV

• MEV extraction on public blockchains isn't generally illegal. Public blockchains let anyone see pending transactions, and their protocols let block producers order transactions however they choose. Some practices, like front-running, resemble activity that's prohibited in traditional securities and commodities markets, and regulators haven't set clear rules for blockchain MEV. In the US, prosecutors charged two brothers in May 2024 over a $25 million exploit that targeted MEV bots, and their first trial ended in a mistrial in November 2025. This is not legal advice.

MEV extraction on public blockchains isn't generally illegal. Public blockchains let anyone see pending transactions, and their protocols let block producers order transactions however they choose. Some practices, like front-running, resemble activity that's prohibited in traditional securities and commodities markets, and regulators haven't set clear rules for blockchain MEV. In the US, prosecutors charged two brothers in May 2024 over a $25 million exploit that targeted MEV bots, and their first trial ended in a mistrial in November 2025. This is not legal advice.

• All MEV is not necessarily a result of an attack or bad actor. Arbitrage keeps prices consistent across decentralized and centralized exchanges, and liquidations keep lending protocols solvent. Sandwich attacks and front-running are the forms that take value directly from traders.

All MEV is not necessarily a result of an attack or bad actor. Arbitrage keeps prices consistent across decentralized and centralized exchanges, and liquidations keep lending protocols solvent. Sandwich attacks and front-running are the forms that take value directly from traders.

• Front-running is a single trade placed ahead of someone else's pending transaction, while a sandwich attack adds a second trade right after it. The second trade lets the bot sell into the price move the victim's swap caused, which is why sandwiches take value from traders more directly.

Front-running is a single trade placed ahead of someone else's pending transaction, while a sandwich attack adds a second trade right after it. The second trade lets the bot sell into the price move the victim's swap caused, which is why sandwiches take value from traders more directly.

• A swap was likely sandwiched if a block explorer shows a buy of the same token just before it and a sell just after, both from the same address. Some MEV analytics sites, such as EigenPhi, let users search by transaction.

A swap was likely sandwiched if a block explorer shows a buy of the same token just before it and a sell just after, both from the same address. Some MEV analytics sites, such as , let users search by transaction.

• Any network where someone decides transaction order have MEV, including Ethereum, Solana, BNB Chain, layer 2 networks and, in more limited forms, Bitcoin. Research has focused mainly on Ethereum, but sandwich attacks are common on Solana, while Bitcoin's MEV mostly comes from fee bidding and transaction ordering.

Any network where someone decides transaction order have MEV, including Ethereum, Solana, BNB Chain, layer 2 networks and, in more limited forms, Bitcoin. Research has focused mainly on Ethereum, but sandwich attacks are common on Solana, while Bitcoin's MEV mostly comes from fee bidding and transaction ordering.

• No. Simple token transfers between wallet addresses rarely attract MEV, because they don't move a market price. MEV mostly targets swaps, liquidations, NFT mints and other trades that change prices on a decentralized exchange or lending protocol.

No. Simple token transfers between wallet addresses rarely attract MEV, because they don't move a market price. MEV mostly targets swaps, liquidations, NFT mints and other trades that change prices on a decentralized exchange or lending protocol.

• A sandwich attack can take up to the slippage tolerance a trader sets, so a wide slippage tolerance on a large trade gives bots more room to profit. Setting slippage tolerance as low as the trade allows limits what a bot can take through MEV.

A sandwich attack can take up to the slippage tolerance a trader sets, so a wide slippage tolerance on a large trade gives bots more room to profit. Setting slippage tolerance as low as the trade allows limits what a bot can take through MEV.

This Article is written by:

• MetaMaskMetaMask, formerly Consensys Software Inc, is the world's largest self-custodial financial platform, giving people a single place to hold, spend, save and grow their money across both crypto and traditional assets. The company is building the consumer platform where that happens, bringing payments, savings, investing and digital assets together in one seamless experience. Having grown from the world's most widely used self-custodial wallet, MetaMask gives users direct control over their money and assets, with reach across approximately 190 countries. MetaMask has played a foundational role in Ethereum's growth since 2016. Today, MetaMask sits at the center of the blockchain economy, building the operating system for Open Money and putting people in full control of their financial lives.Read all articles

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