What Is the Significance of the ‘Nonce’ in Bitcoin Mining?

The nonce (Number Once) is a 32-bit field in the Bitcoin block header that miners iterate on to find a valid block hash. Since all other block header fields (like the Merkle root and timestamp) are essentially fixed for a given mining attempt, the miner changes the nonce value to generate a new block hash.

This brute-force process is the core of the Proof-of-Work mechanism, demonstrating the computational effort expended.