validator

A validator is a participant in a proof-of-stake blockchain who has locked up a deposit in order to help run the network — proposing new blocks, checking other people's blocks, and voting on which chain is the real one. Validators are the proof-of-stake counterpart to proof-of-work miners: both keep the ledger honest, but a validator earns the right to do so by putting capital at risk rather than by spending electricity.

A validator's job runs in two modes. Some of the time the network randomly selects it to be the block proposer: it gathers pending transactions, assembles the next block, and broadcasts it. The rest of the time it acts as an attester, examining blocks proposed by others and signing off that they follow the rules. These signatures, gathered from many validators, are how the network reaches agreement on each block — a kind of continuous, weighted vote.

The deposit is what keeps a validator honest. Follow the rules and it collects steady rewards; break them — by going offline at the wrong moment, or by signing two conflicting blocks — and part of its stake can be automatically destroyed, a penalty called slashing. Because misbehaving directly burns the validator's own money, the cheapest path is almost always to behave, which is exactly how a crowd of self-interested validators ends up securing the chain for everyone.