COLORFIGURE / ETHEREUM
One slot, many possible paths

How an Ethereum block gets built

Transactions arrive. Someone orders them. A validator proposes one block. The network checks it—and later, consensus finalizes it.

Important: MEV-Boost is an optional, out-of-protocol market used by many proposers. It is not the only way to build an Ethereum block, and private order flow is never assumed.

READY / choose a step0 of 6
Ethereum block-building pipelineA hand-drawn isometric pipeline from transaction sources through builders and relays to a validator, then to the Ethereum network and finality. PUBLIC MEMPOOLbroadcast transactions PRIVATE ORDER FLOWoptional · routing varies SEARCHERS + BUILDERsimulate · order · bid RELAY(S)check bids · serve header VALIDATOR PROPOSERchooses · signs · proposes PROPAGATE + VALIDATE LATER: FINALITY BID + HEADER SIGNED BLINDED FULL PAYLOAD
Pick a route, then step through the machine.
1

Transactions

Most users broadcast to the public mempool. Some use private RPCs or other private routes. A transaction’s path depends on the wallet, RPC and service.

2

Search & build

Searchers may send bundles. Builders simulate candidates, combine available order flow and construct a complete execution payload with a bid.

3

Propose

With MEV-Boost, relays check builder submissions and expose bids. The proposer signs a blinded beacon block before the winning payload is revealed.

4

Agree

The proposed block propagates. Nodes validate it; attestations add consensus weight. Finality comes later through proof-of-stake consensus—not from the builder market.

DEPLOYED TODAY

MEV-Boost: outside the protocol

MEV-Boost is optional middleware between a validator’s consensus client and one or more relays. It creates out-of-protocol proposer-builder separation without changing Ethereum’s base protocol.

  • Builders and relays are external actors.
  • The proposer can still choose a locally built payload.
  • Trust, liveness and censorship tradeoffs differ by relay and configuration.
FUTURE / PROPOSED

Protocol PBS: still evolving

“Enshrined” or protocol PBS refers to designs that move builder-market mechanics into Ethereum’s protocol. It should not be presented as the system running today.

  • Exact design and deployment path remain research topics.
  • Future protocol roles and messages may differ from MEV-Boost.
  • This figure intentionally keeps that path separate.

Sources & scope

  1. Flashbots — MEV-Boost overview: describes optional, out-of-protocol PBS and the builder marketplace.
  2. Ethereum Builder API specification: canonical request/response interface used by MEV-Boost and relays.
  3. Ethereum.org — Proof of stake: proposer, attestation, consensus and finality context.
  4. Ethereum.org — Proposer-builder separation roadmap: protocol PBS research and roadmap framing.

Visual grammar inspired by April Zhu’s Colorfigures, MIT licensed; built on ISO-GLOW by April Zhu and iso-figure by Tolga Cohce. This clean implementation does not embed or execute the downloaded skill code. Educational overview, not a timing diagram or guarantee of inclusion.