What is block proposer?

The single validator selected for a given slot and permitted to publish a block in it.

Selection is pseudorandom and weighted by stake, and the proposer collects the transaction tips and any builder payment for that block, which is why proposal rewards are lumpy while attestation rewards are steady (source: the Ethereum consensus specifications). A proposer that is offline or late simply leaves the slot empty; the chain continues at the next one.

Most proposers today take a block from an outside builder rather than assembling one themselves, which is the single most consequential thing about the role in practice.

How it works

Duties are assigned an epoch ahead. That lets an operator prepare, and it also lets everyone else see who is next, a trade-off the design accepts deliberately.

The proposer's job is to publish one block in its slot. If it publishes late, attesters may have already voted for an empty slot, and the block is orphaned even though it was valid.

Rewards split into two kinds. Attestation rewards accrue to every validator every epoch and are small and predictable. Proposal rewards arrive only in the slots you are selected for, and they include the priority fee tips in the block, so a single busy slot can pay more than months of attesting.

Under mev boost, the proposer outsources block construction. Builders compete in an auction to supply a block, bidding a payment to the proposer, and the proposer signs a header committing to the highest bid before seeing the contents. This raises proposer income and moves transaction ordering to a small set of builders.

Because the base fee is burned rather than paid to anyone, the proposer's share of user fees is the tip only.

Example

Illustrative: a validator with 32 ETH staked is selected as proposer roughly once every few months, depending on the total number of active validators. Attesting earns a small amount each epoch throughout. In one selected slot, the block carries $400 of priority fees and a builder bid of $110. The proposer receives that in a single slot, while the base fee portion of every transaction in the block is destroyed. Figures are illustrative.

Why it matters when you buy

Proposers decide which transactions land and in what order within their slot, which is where transaction ordering costs like a sandwich attack come from. If you buy on a decentralized venue, that ordering is a real cost in your fill. Buying on a centralized exchange sidesteps it entirely, since the trade never touches a public mempool. Compare the two approaches at the guide on centralized versus decentralized exchanges.

Related terms

• validator — the pool proposers are drawn from
• slot — the interval a proposer is assigned
• mev boost — the auction most proposers use
• priority fee — the tips a proposer keeps
• beacon chain — the layer that assigns duties
• epoch — the period duties are assigned across

Questions

Can a proposer censor my transaction?

A single proposer can exclude it from one block, delaying it by a slot. Sustained censorship would require most proposers to cooperate, and any non-censoring proposer includes the transaction at the next opportunity.

Why are staking rewards uneven?

Because attestation rewards are steady and proposal rewards are rare and large. Pooled staking products smooth this by averaging across many validators.

Does the proposer choose transaction order?

Formally yes, but in practice most delegate construction to a builder through an auction and sign whatever ordering that builder produced.