A validator node runs the software and signing infrastructure used to perform a blockchain’s assigned consensus duties. Depending on the protocol, those duties include proposing blocks, checking proposed state changes and signing votes that help the network agree on its history.
Participation and node roles
In proof-of-stake systems, an active validator is associated with staked assets and must meet the protocol’s eligibility requirements. Permissioned systems may instead authorize selected participants. A full node can independently check blocks without holding an active validator role; verifying data and casting consensus votes are related but distinct activities.
Ethereum, for example, uses execution and consensus clients together with validator software for signing duties. An operator can manage multiple validator keys, so the number of validators is not necessarily the number of independent operators or physical machines.
Operational responsibilities
Reliable connectivity, current client software and protected signing keys matter because missed duties can reduce rewards or incur protocol-specific penalties. Slashing applies to specified violations, such as conflicting signatures in protocols that punish them; it is not a universal name for every outage penalty.
Running a validator does not guarantee income or grant unrestricted control over transactions. Hardware costs, token-price changes, software failures and concentration among operators can affect both participants and network security.