Attestation

An attestation is a signed vote a validator broadcasts to affirm its view of the chain — most prominently on Ethereum, where attestations declare which block is the correct head of the chain and which checkpoints should be justified and finalized. Attestations are the raw material of proof-of-stake consensus: blocks become canonical and eventually final because a supermajority of staked ether attests to them.

On Ethereum, every active validator is expected to attest once per epoch (roughly every 6.4 minutes), in an assigned 12-second slot. The attestation names the current head block plus source and target checkpoints, and is signed with the validator's key. For example, when a validator sees a newly proposed block at slot 100, it publishes an attestation endorsing that block; aggregators combine thousands of such signatures into compact aggregates that fit inside the next blocks. Validators earn small rewards for timely, correct attestations and are penalized for missing them — and slashed severely for signing contradictory ones, since conflicting votes are treated as an attack on consensus.

A common misconception is that only block proposers matter in proof of stake; attesting is the far more frequent duty, and the steady stream of attestations — not block production — is what accumulates the votes needed for finality. The word also appears in unrelated crypto contexts, such as stablecoin "reserve attestations" by accountants; in consensus discussions, though, an attestation always means a validator's signed vote.