Validator

A validator is a participant in a Proof of Stake blockchain network whose job is to verify new transactions, propose new blocks, and vote on the correctness of the chain. The term is the PoS equivalent of a miner in Proof of Work systems. While miners compete through computational work, validators are selected based on the amount of cryptocurrency they have staked — locked up as collateral — and earn rewards for performing their duties honestly and consistently.

On Ethereum, becoming a validator requires staking exactly 32 ETH. Once active, a validator runs special software that stays connected to the network at all times, checking transactions’ validity and periodically being assigned to propose a new block or participate in a committee that votes on a recently proposed block. If a validator is offline too often, they gradually lose a small portion of their stake through an inactivity penalty. If they actively try to cheat — for example by simultaneously signing two different blocks — they face slashing, which can destroy a significant portion of their locked funds.

Example: A validator is like a notary public for the blockchain. Their job is to check that documents (transactions) are legitimate, stamp them as approved, and add them to the official record. Just like a notary puts their professional license on the line when they certify a document, a validator puts their staked cryptocurrency on the line every time they vouch for a transaction.