A validator is a blockchain user or network participant who contributes to verifying transactions and producing new blocks. Most commonly found in blockchains using a proof of stake consensus mechanism, validators are nodes that store a record of the entire blockchain or a limited version of the distributed ledger on their end-user devices.
These validators then offer computing power and storage resources for block production, to verify new transactions, and to record them in new blocks. Once a new block is created and added to the blockchain at a validator node's end, the validator is responsible for communicating this change to all other validators within the network. This ensures that all validator nodes have access to the latest blockchain version at their respective ends.
In addition to verifying transactions, validators are also responsible for ensuring that the transactions’ format is correct. They also compute the hash fingerprints across each block to confirm the right state of the blockchain network. Finally, they also validate each new block added to the distributed network to ensure the correctness of the block structure and mining puzzle solving.