Definition
The block header is the compact summary of a block that miners repeatedly hash when searching for a valid proof of work. It contains exactly six fields totaling 80 bytes: version (4 bytes), previous block hash (32 bytes), Merkle root (32 bytes), timestamp (4 bytes), bits/target (4 bytes), and nonce (4 bytes).
Miners hash this 80-byte header using double SHA-256. By changing the nonce (and sometimes the timestamp or Merkle root via the extra nonce), they produce different hash outputs until they find one below the difficulty target.
In Simple Terms
The 80-byte section of a block that miners hash. Contains version, previous hash, Merkle root, time, target, and nonce.
Block Header is a term used in Bitcoin mining related to mining basics.
The block header is the compact summary of a block that miners repeatedly hash when searching for a valid proof of work. It contains exactly six fields totaling 80 bytes: version (4 bytes), previous block hash (32 bytes), Merkle root (32 bytes), timestamp (4 bytes), bits/target (4 bytes), and nonce (4 bytes).
Miners hash this 80-byte header using double SHA-256. By changing the nonce (and sometimes the timestamp or Merkle root via the extra nonce), they produce different hash outputs until they find one below the difficulty target.
Understanding block header is important for Bitcoin miners because it directly impacts mining operations, hardware selection, or profitability calculations. Whether you are a home miner running a Bitaxe or operating a larger ASIC setup, this concept helps inform better mining decisions.
Related terms: Nonce, Merkle Root, Block, SHA-256, Target, Bits.