Block Height

Block height marks a block's exact position in a blockchain, counted as the total number of blocks confirmed before it, starting from the genesis block, which sits at height zero. Every subsequent block references the hash of its predecessor, so the count rises by exactly one with each new addition, leaving no gaps or skipped numbers in the sequence.

Nodes use block height as a synchronization check: if a node's local height matches the height its peers report, it holds a complete, current copy of the chain. Block explorers surface height prominently because it works as a fixed reference point in time. On Bitcoin, the halving that cuts the mining block reward in half is scheduled by height rather than calendar date, happening every 210,000 blocks; mining difficulty also recalculates every 2,016 blocks to keep average spacing near ten minutes. Some wallets and smart contracts use height-based locktimes, releasing funds or executing logic only once the chain reaches a specified block.

Height is useful but imperfect as a unique identifier. Near the tip of the chain, two miners can occasionally produce competing blocks at the same height; a chain reorganization then resolves which one the network keeps, meaning the block occupying that height can briefly change. Once a block sits several confirmations deep, this risk becomes negligible. Because block time varies by network, comparing raw heights across different blockchains says little on its own; Bitcoin, for example, had passed height 950,000 by mid-2026, while faster chains reach far higher numbers over the same real-world time.