MEV-Boost
MEV-Boost is the middleware implementing proposer-builder separation on Ethereum: validators outsource block construction to specialized builders via relay
MEV-Boost is the middleware implementing proposer-builder separation on Ethereum: validators outsource block construction to specialized builders via relays, accepting the most profitable header blindly. It now produces the large majority of Ethereum blocks.
How it works
Builders assemble MEV-optimized blocks and bid through relays; the proposer’s validator signs the winning header without seeing contents (protecting against theft); payment settles on-chain to the proposer. Relay diversity is the whole decentralization story.
Why it matters for decentralization
MEV-Boost democratized MEV *revenue* (solo validators earn like pros) while concentrating MEV *power* (a few builders + relays construct nearly everything). Censorship compliance at the relay layer (OFAC-filtering relays dominating share) proved the risk is real, not theoretical. Relay diversity and enshrined PBS are the fixes being built.
Risks & trade-offs
Relay oligopoly and censorship; builder centralization outpacing validator decentralization; timing games; and the uncomfortable truth that “neutral” infrastructure keeps needing patches against its own economics.
FAQ
Must validators use MEV-Boost? No — it’s opt-in middleware. Opting out means leaving significant revenue on the table, which is why adoption is near total despite being voluntary.
Does it hurt Ethereum? It centralizes block *building* while keeping *proposing* decentralized — better than the alternative (integrated builder-proposers), worse than the ideal (many builders).
What fixes it? Enshrined PBS (protocol-level separation) plus encrypted mempools — removing trusted relays from the loop entirely.