With regard to blockchains such as Bitcoin and Ethereum (until September 2022) that use a proof-of-work (PoW) consensus mechanism, validators are computers dedicated to maintaining a blockchain's integrity. Validator nodes may store the full blockchain or an abbreviated version that is quicker to analyze. Validators for a public blockchain are maintained primarily by volunteers, who typically dedicate a computer to the process, and there are thousands of such nodes for a major blockchain such as Bitcoin and Ethereum.
Testing Format, Linkage and Puzzle
Validator nodes perform three functions: #1 - checking the layout of new transactions to make sure they are formatted correctly, #2 - computing the hash fingerprints from block to block to ensure nothing on the chain was altered, and #3 - validating each new block to make sure the miner's puzzle was solved correctly and the block is structured properly. See
mempool and
consensus mechanism.
Ethereum 2.0 (Eth2) Changed Consensus Methods
In September 2022, Ethereum changed its consensus mechanism from proof-of-work (PoW) to proof-of-stake (PoS), and Ethereum miners became Ethereum validators in Eth2. Validators of proof-of-stake blockchains, such as Ethereum 2.0, Solana and Cardano, win the right to place the next block of transactions on their respective blockchain based on randomness and the amount of native crypto put up as collateral. See
Bitcoin,
Ethereum 2.0,
Solana,
Cardano,
blockchain,
crypto miner and
proof-of-stake algorithm.