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Configure MEV aka Proposer Builder Separation

Proposer Builder Separation​

MEV Boost​

Your Consensus Layer client connects to the mev-boost container. If you are running a CL in Eth Docker, then in .env you'd add mev-boost.yml to COMPOSE_FILE, set MEV_BOOST=true and set MEV_RELAYS to the relays you wish to use.

Commit Boost​

This is an alternative to MEV Boost. Your Consensus Layer client connects to the cb-pbs container. If you are running a CL in Eth Docker, then in .env you'd add commit-boost-pbs.yml to COMPOSE_FILE, set MEV_BOOST=true and set MEV_NODE=http://cb-pbs:18550.

Next, edit commit-boost/cb-config.toml and configure the relays you'd like to use.

Verify​

If you would like to verify whether your MEV relay has registered your validator, follow the documentation for your chosen relays. For instance, if you have included Flashbots, you can see whether your validator has been registered by querying their API. Add your validator's public key to the end of this endpoint: https://boost-relay.flashbots.net/relay/v1/data/validator_registration?pubkey=

Just a VC, example RocketPool​

If you are running a validator client only, such as with a RocketPool "reverse hybrid" setup, then all you need to do is to set MEV_BOOST=true in .env. mev-boost.yml and MEV_RELAYS are not needed and won't be used if they are set, as they are relevant only where the Consensus Layer client runs. See the Overview drawing for how these components communicate.

Building locally​

You have the option of building local blocks, when remote blocks don't pay enough for your liking. Depending on your VC (Validator Client), you may already be doing that, in fact!

Two parameters in .env control this behavior.

MEV_MIN_BID, set to an ETH value, e.g. 0.003. Unless a remote block pays more than this, you build locally.

MEV_BUILD_FACTOR, set to a percentage cutoff point. Several VCs default to 90, which means "unless remote pays at least 10% more, build locally". 100 has a special meaning in Eth Docker and means "always build remote". The in-protocol value for this is 18446744073709551615, which Eth Docker sets "under the hood" when it sees 100.

Since the Fusaka hard fork in December 2025, local block building may require large upload bandwidth, up to 200 Mbit/s. Restricting the number of blobs to include when building locally would resolve this, but that functionality is not yet present as of February 2026. If your upload bandwidth is constrained, MEV_BUILD_FACTOR=100 can make sense.