Nonce

A nonce is a number used once, a value miners or wallets change to produce a different result each time. In mining, it lets a miner keep guessing until a block's hash meets the network's difficulty target. In wallets, a nonce tracks transaction order so the same signed transaction can't be replayed twice. Readers run into it often without realizing: an Ethereum wallet showing "nonce too low" simply means a transaction with that sequence number already went through. For example, Bitcoin's mining nonce is a 32-bit field, so miners exhaust roughly 4 billion guesses before adjusting other block data and trying again. It's a small detail that keeps both mining and account security working correctly.