Definition
A block header is the fixed-structure metadata section at the beginning of a blockchain block that summarizes key information about the block. It typically includes references to the previous block, a representation of the block’s transactions, a timestamp, and consensus-related fields such as difficulty and nonce. The block header is the part of a block that is repeatedly hashed and validated by network participants.
In Simple Terms
A block header is the summary card at the front of a block. It holds the essential data that identifies the block, links it to the previous one, and represents the transactions inside it. This compact data is what nodes use to recognize and verify the block within the blockchain.
Context and Usage
The term block header is commonly used when discussing block structure, consensus mechanisms, and validation in blockchain systems. It appears in technical documentation, protocol specifications, and discussions about mining, difficulty adjustments, and hash rate measurements. Developers, node operators, and protocol researchers refer to the block header when analyzing how blocks are identified, linked, and checked for correctness.