What is Block Header?
The block header is a fixed-size summary containing the previous block hash, Merkle root of transactions, timestamp, difficulty target and nonce. Miners hash the header (not the full block) when searching for a valid Proof of Work.
Why Block Header matters
Understanding Block Header is part of building a solid mental model of how Bitcoin, blockchain and Web3 systems actually work. Concepts in the Bitcoin category sit at the foundation of the broader stack — get them right and the rest is far easier.
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Related terms
- Block — A bundle of transactions added to the blockchain.
- Merkle Root — The single hash summarising all transactions in a block.
- Nonce — The number miners change while searching for a valid hash.
- Proof of Work — A consensus mechanism that requires computational work to add blocks.
More bitcoin terms
- Address (Bitcoin / Crypto Address) — A public destination for receiving cryptocurrency.
- Block Reward — New coins paid to the miner of a block.
- Difficulty — A parameter that controls how hard it is to mine a block.
- Double Spend — Attempting to spend the same coin twice.
- Halving — The scheduled 50% cut in Bitcoin's block subsidy.
- Hash Rate — The total computational power securing the network.
- Mining — Producing new blocks by performing Proof of Work.
- Nakamoto Consensus — Bitcoin's consensus rule: follow the chain with the most work.
Keep exploring
Continue with the full blockchain glossary — 136 terms in total — or read the developer blog and FAQ for deeper context.