In blockchain technology, ‘block depth’ refers to the number of blocks mined after a specific block. Conversely, ‘block height’ refers to the number of blocks that preceded the block in question.
These measurements are important in certain blockchain hashing algorithms such as Bitcoin’s (BTC) Block depth use them as part of their calculations when auto-adjusting the mining difficulty. This is part of the hash rate calculation, so as to ensure that each block is completed in no more or less than 10 minutes. Another function of block depth is block confirmation. In instances of a fork with dead chains, the nodes of a decentralized blockchain will use a consensus algorithm to determine which chain should be added to and which is defunct.
Block height, on the other hand, is used for either pinpointing data within a blockchain or to determine the blockchain’s current length. It is calculated from the genesis block, which is the first block ever in a blockchain. There are also many other functions, such as Bitcoin halving, whereby the mining reward is halved every 210,000 blocks. This is why the 21 million BTC cap will only be reached in the year 2140. Even then, this is a theoretical endpoint point, as the reward should continue as a tiny decimal of a Satoshi. However, the reward will be so insignificant that it may was well be the full 21 million BTC. Additionally, transactions can be set up to only unlock at a specific block height or UTC time. This is called a timelock.