Block Height

Block height is the position of a block in a blockchain, counted as the number of blocks between it and the very first block. The first block — the genesis block — sits at height 0, the next at height 1, and so on, so the current block height also tells you how many blocks have been added since the chain launched. Because every block references its predecessor, height is an unambiguous coordinate: saying "the transaction confirmed at height 800,000" pinpoints exactly where in Bitcoin's history it happened.

Height is used constantly in practice. Protocol upgrades and halvings activate at predetermined heights rather than calendar dates — Bitcoin's block subsidy halves every 210,000 blocks, so the 2024 halving occurred at height 840,000. Explorers, wallets, and smart contracts use height to schedule events, measure confirmations (current height minus your transaction's height), and reference chain state at a moment in time.

A common misconception is that height maps precisely to time; block intervals are only statistical targets — roughly ten minutes for Bitcoin, twelve seconds for Ethereum — so converting a future height to a date is always an estimate that drifts. Another subtlety: during a temporary fork, two competing blocks can briefly share the same height until the network converges on one branch, which is why applications that need certainty wait for additional blocks to be built on top rather than trusting the newest height alone.