What it is in Bitcoin
In Bitcoin, the blockchain is the append-only ledger: a linear chain of blocks from the genesis block to the tip, each block committing to transactions and linking to the previous block hash. That link makes history tamper-evident — changing an old transaction changes its block’s hash, which breaks every later block unless all following PoW is redone.
[[en/books/inventing-bitcoin|Inventing Bitcoin]] warns the word is overused in marketing; in Bitcoin it is simply the data structure that orders issuance and spending.
Consensus and copies
Thousands of participants hold identical copies synchronized by the protocol. The consensus algorithm compares work; users do not vote by headcount — a single honest peer with the most-work valid chain suffices for a new node to find the true tip if it is not eclipsed from the honest network.
Skeptical framing from the same corpus
[[en/books/sovereignty-through-mathematics|Sovereignty Through Mathematics]] argues the important invention is Bitcoin’s consensus rules solving the Byzantine generals problem — “blockchain” without those rules is often hype.
Sources
Related pages
- Bitcoin — how the blockchain fits the full system
- Mining — how new blocks are produced
- Proof of Work — the mechanism that makes the chain tamper-evident
- Double spend — what transaction ordering prevents
- Forks — competing tips and chain reorgs
- Mempool — where transactions wait before inclusion
- Bitcoin node — who validates blocks
- UTXO — the accounting model stored in the chain