The number of blocks preceding a particular block in a blockchain.
Block height refers to the number of blocks preceding a particular block in a blockchain. It is essentially the length of the blockchain minus one, as the genesis block (the first block in the blockchain) has a height of zero. Each new block added to the blockchain increases the block height by one.
Block height serves as a sequential identifier and timestamp for blockchain events. It's often used as a reference point for software upgrades, protocol changes, and to track the chronological progress of the network. Understanding block height is crucial for developers implementing blockchain applications and for users tracking transaction confirmations.
As of late 2023, the block height of the Bitcoin (BTC) blockchain exceeds 800,000 blocks, with a new block being added approximately every 10 minutes, thereby increasing the block height by one. You can reference specific moments in Bitcoin's history by block height, such as the first halving which occurred at block 210,000.
Activation of features or changes to the blockchain usually occur at specific block heights. For instance, Bitcoin's block reward halvings happen at predetermined block heights approximately every 210,000 blocks (roughly every four years). Similarly, when Bitcoin Cash (BCH) undergoes upgrades, the features are activated at predetermined block heights to ensure network synchronization. The SegWit upgrade on Bitcoin was activated at block height 477,120.
When someone says a transaction has "6 confirmations," it means that since the block including your transaction was added, 6 more blocks have been added to the chain, increasing the block height by 6. The higher this number, the more secure the transaction is considered.
In a broader sense, the block height can also refer to the total number of blocks confirmed on a blockchain. This metric is commonly used to assess the maturity and operational history of a blockchain network. Block explorers prominently display the current block height as a key statistic of the network's status.
During blockchain forks or network synchronization issues, nodes may report different block heights. This inconsistency typically indicates that consensus has temporarily broken or that some nodes are lagging behind the current state of the blockchain.
All terms and definitions may update as the Cryptionary improves.