On a proof-of-stake blockchain, a validator is a participant who has locked up ("staked") the network's native coin as collateral and taken on the job of proposing and attesting to new blocks. Validators are chosen to produce blocks in a pseudo-random process weighted by their stake.
In return for honest work, validators earn newly issued coins and a share of transaction fees. If they go offline or try to cheat, the network can "slash" — permanently destroy — part of their staked collateral. That economic threat is what secures a proof-of-stake chain.
Most regular users never run a validator directly, staking instead through a pool or a liquid-staking protocol that aggregates smaller amounts. Running a validator typically requires meeting a minimum stake threshold and keeping a node online continuously.
Worked example
Ethereum requires 32 ETH to run a solo validator; smaller holders can delegate to a pool such as Lido instead.
Related guides
This definition is general education, not investment advice. Markets — especially crypto — are volatile and you can lose money. Please read our disclaimer and see our methodology.