Block height refers to the total number of blocks confirmed on a blockchain since the first block, known as the genesis block (#0). Each new block links to the hash of the block before it, forming a continuous chain. For example, the genesis block is height 0, while the first mined block is height 1.

You can think of block height like a stack of Lego bricks: once stacked, you can’t remove one from the middle without disrupting the entire structure.

In practice, block height grows as new blocks are mined or validated. For Bitcoin, with an average block time of 10 minutes, the block height reflects how many blocks have been added since 2009. Other blockchains have different block times, so comparing heights directly between networks can be misleading.

Block height is also a useful measure to check if your local blockchain copy is synchronized with the global network. If the heights don’t match, your copy is out of sync and missing the latest blocks.