A distributed, immutable ledger that records every Bitcoin transaction in sequential blocks linked by cryptographic hashes. The blockchain enables trustless verification without any central authority.
A distributed, immutable ledger that records every Bitcoin transaction in sequential blocks linked by cryptographic hashes. The blockchain enables trustless verification without any central authority.
A blockchain is a chain of data blocks, each containing a batch of validated transactions. Every block includes a cryptographic hash of the previous block, creating an unbreakable chain back to the genesis block mined by Satoshi Nakamoto on January 3, 2009. This structure means that altering any historical block would invalidate every subsequent block, making the ledger tamper-proof.
Bitcoin's blockchain is maintained by a decentralized network of nodes that independently verify every transaction and block. When a miner finds a valid block, it is broadcast to the network. Each node checks the block against the consensus rules — correct proof-of-work, valid transactions, proper block reward — before adding it to their local copy of the chain. This redundancy means no single point of failure can corrupt the record.
The Bitcoin blockchain produces a new block approximately every 10 minutes, with the difficulty adjustment ensuring this cadence regardless of how much mining power joins or leaves the network. As of 2024, the blockchain contains over 800,000 blocks and stores the complete history of every Bitcoin transaction ever made. Its transparency allows anyone to audit the total supply, verify transactions, and analyze on-chain metrics used by indicators like MVRV Z-Score.
A traditional database is controlled by a single entity that can modify or delete records. The Bitcoin blockchain is distributed across thousands of independent nodes worldwide, and its cryptographic structure makes altering past records computationally infeasible. No single party can censor transactions, reverse payments, or change the rules without consensus from the network.
Altering the blockchain would require controlling more than 50% of the network's total mining power (a "51% attack") and sustaining that majority long enough to rewrite blocks. Given Bitcoin's enormous hash rate — the largest computing network on Earth — this is economically impractical. The cost of such an attack would far exceed any potential gain, and the attacker's own holdings would be devalued in the process.
The full Bitcoin blockchain is over 600 GB as of 2024 and grows by roughly 50-80 GB per year. Running a full node requires downloading and verifying this entire history. Pruned nodes can verify everything but discard old block data to save disk space, while SPV (lightweight) wallets verify only block headers and rely on full nodes for transaction data.