In cryptography, a nonce is an arbitrary number that can be used just once in a cryptographic communication. It is similar in spirit to a nonce word, hence the name. A Bitcoin nonce is an arbitrary number that is used in Bitcoin’s proof of work consensus algorithm. The nonce can be found as a 4-byte field in a block header, and sees its value adjusted by miners so that the hash of the block will be less than or equal to the current target hash value set by the network.