Flashbots is the research organization and software project that built the dominant MEV infrastructure on Ethereum. The two pieces a US-resident holder will encounter are Flashbots Protect (a private-RPC endpoint that hides your transactions from public-mempool searchers) and MEV-Boost (the validator-side relay that auctions block-construction to specialized builders). Both are free to use, both materially improve execution quality for retail DEX traders.
The problem Flashbots solves on the user side
When you submit a transaction via the standard Ethereum RPC (Infura, Alchemy, public nodes), the transaction enters the public mempool. Anyone watching the mempool — and many actors are — can see your pending DEX swap, calculate the optimal sandwich attack, and execute it within the same block.
Flashbots Protect routes your transaction directly to block builders without exposing it in the public mempool. Searchers cannot see it; they cannot sandwich it. The execution is private until the block lands on chain.
How to actually use it
Configure your wallet's RPC endpoint to point at Flashbots Protect:
https://rpc.flashbots.net
In MetaMask: Settings > Networks > Ethereum Mainnet > edit RPC URL. In Rabby: Settings > Networks > Edit > custom RPC. The change is invisible after setup — transactions submit normally, they just take a different path to the block.
The trade-off: transactions might take slightly longer to confirm (Flashbots batches and submits in blocks; the typical extra delay is one block, roughly 12 seconds). For DEX trading and any sandwich-vulnerable activity, this is a clear net win. For time-sensitive arbitrage by retail users, it might cost an opportunity.
The validator-side architecture
MEV-Boost, deployed in October 2022 alongside Ethereum's transition to proof-of-stake, separates validator duties from block-builder duties. Validators run MEV-Boost as a sidecar; it receives blocks from specialized builders (Flashbots being one of several) and the validator selects the highest-bid block to propose.
This separation matters because it lets searchers compete to extract MEV efficiently while validators capture a share of the value without needing to run searcher infrastructure themselves. Post-merge Ethereum economics — validator yield, staking returns, the entire ETH issuance reduction — depends materially on this architecture.
The censorship debate
After OFAC sanctioned Tornado Cash in August 2022, some MEV-Boost relays (including Flashbots' own) began filtering Tornado-related transactions from blocks they propose. Over the following months, the percentage of OFAC-censoring blocks rose to about 80% of Ethereum block production at peak.
This raised the question of how decentralized Ethereum's block production actually is. The community responded by building alternative non-censoring relays (Ultra Sound Relay, Agnostic Relay) and pressuring validators to use them. The OFAC-censoring percentage has since dropped to roughly 30-40% as of 2026, though it varies week to week.
For a US-resident holder, this is mostly irrelevant — your transactions are not OFAC-flagged. It matters as a signal about the resilience of Ethereum's neutrality. Holders who care about that property should know about it.
The 2026 landscape
Flashbots remains the largest MEV ecosystem player but is no longer monopolistic. Other private-RPC services (MEV Blocker, BloXroute Protect, Manifold Protect) offer similar features. CoW Swap's batch auctions provide MEV protection at the protocol layer rather than the RPC layer. The trend is more competition, more choice, and lower retail MEV taxes.