The most basic description of block height is that it is an expression of the total number of individual blocks that are a part of a specific blockchain. You might even think of it as “block length,” as it expresses the size of the blockchain, or if this were a literal chain, then how many links there were.
Perhaps most importantly, block height indicates how steadily new blocks are being discovered and added to a specific blockchain over time.
If you visit a blockchain explorer, you will find a lot of detailed information about multiple blockchains. Among the information available, you will see the block height.
Central to the functionality and preservation of any cryptocurrency is the maintenance of the blockchain that it is a part of. Remember, cryptocurrencies are not physical coins or stores, they are collections of encrypted transactions stored on a blockchain, and are maintained by the decentralized networks.
Cryptocurrencies work on blockchains that are composed of a sequence of blocks. Each block contains information that links it to the past block and qualifies as part of the blockchain.
The most current block in a chain will contribute to the next block in the chain. Within each block is a collection of data which stores information about a transaction on that network.
The block height of a particular block, therefore, indicates how many blocks preceded any individual block, as part of the whole blockchain. For example, if you are looking at a block height of 235, then there are 235 blocks ahead of it in the sequence.
This is because when counting blocks, the count actually begins with number 0 (zero) on a blockchain. The first block is referred to as the genesis block. It is called the “genesis block” because it is the block that is responsible for the origin of a blockchain.
To learn more about genesis blocks on our blog: What is a Genesis Block
When a miner has successfully hashed a block header, the block is added to the blockchain. An individual block can be identified by its block height. However, it is possible for more than one block of the same blockchain to have the same height.
Two blocks will have the same height in the event that more than one miner has simultaneously and successfully produced a block on a blockchain. This actually happens with a certain amount of regularity. When the same block is confirmed more than once, it has the potential to create what is called a “fork.” This happens because there cannot be duplicate blocks on a specific blockchain; this can result in a fork. But the blocks can also be orphaned, which means that they do not end up on the main blockchain.
Read more about orphan and uncle blocks here.
The way this happens is that miners produce blocks simultaneously. It is then the responsibility of each node to choose which block to approve and add to the main blockchain. The block that receives the greatest consensus from the decentralized network is added to the main blockchain.
Read more about forks, on our blog: Guide to Bitcoin Forks
Since multiple blocks can have the same height on a specific blockchain, block height should not be used as a globally unique identifier. The uniqueness of a block is in the hash of its header, not in its height. That means, that the block height is most relevant within the context of its corresponding blockchain.
For example, take Bitcoin’s current block height, which as I am writing this article is, 568324. By contrast, Ethereum’s current height is 7419995. Block height does not give us an identifier of a transaction, nor does it indicate market value. What the height provides us with is the difficulty of mining a block and subsequently, the security and difficulty of a specific currency.
Remember, when you go to check the block height of either of these currencies, you will see a different number then is listed here, as blocks are consistently being added to the blockchain.
In the case of Bitcoin v. Ethereum, because Bitcoin has a more demanding proof-of-work, it takes longer to add a block to the Bitcoin blockchain then it does to Ethereum’s. A new block is added about every 10 minutes to the Bitcoin blockchain. However, in Ethereum’s case, a block is added every 15 seconds.
If you would like to know more about mining and hashing visit: What is Bitcoin Mining
Nevertheless, Block height is a relevant detail for many reasons. One reason is that there is credibility in the size of a blockchain. The length of a blockchain is important because it is one of the details that demonstrates that the participating networks are in agreement about the legitimacy of certain blockchains.
Consensus and block height, are in some ways two sides of the same coin. A central part of the Satoshi Nakamoto’s vision for Bitcoin’s blockchain was to use a hash function that was computationally difficult enough that not every node would to be able to come up with the target hash.
For more on network consensus go here.
As a result, the block height increases as nodes concur on a specific blockchain. So, if example, if someone were to forge a Bitcoin blockchain, they would have to compete with the current block height of the authentic currency; this is essentially impossible. Given the computational power necessary for mining Bitcoin, fabricating a fake blockchain would require an almost incalculable about of energy and processing power.
What is the bottom line for block height?
Block height is at best an easy way to observe the growth and size of a blockchain. But knowing the growth and size of a blockchain relative to itself and to others has its utility. Observing the growth of any cryptocurrency on a blockchain gives us an indication of difficulty, popularity and also hints at the quality of the network consensus.
Height does not give us detailed information about the actual block. However, it does give us a quick way to see how quickly blockchains are growing, as well as gives us another tool to measure and compare our cryptocurrencies.
When it comes right down to it, height is not the most important piece of data listed on a blockchain explorer. Nevertheless, because of the design of cryptocurrency and decentralized networks, it in no way harms the cause to have more information that we can use for analysis of a currency’s authenticity or its general acceptance.