Glossary · Mining Basics
Block header
The block header is the 80-byte summary of a block that miners actually hash, containing the previous block's hash, a Merkle root committing to the block's transactions, a timestamp, the difficulty target and the nonce.
Related terms
- Nonce
- The nonce is a 32-bit field in the block header that a miner changes between hash attempts so that each attempt produces a different hash, with the extra nonce in the coinbase transaction providing more room once the 4.3 billion values run out.
- Proof of work
- Proof of work is the consensus mechanism in which miners repeatedly hash candidate block headers until one produces a value below the network's current target, making each new block expensive to produce and cheap to verify.
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