Block Header

What Is a Block Header?

The block header is a part of a block that summarises the rest of the block. It's composed of all the metadata, including the block's timing and hardness, the Merkle root of the contained transactions, and the nonce. The prior block's hash is also provided and is what enables us to form the "chain" of blocks. 

The block header generally includes any information that isn't a collection of raw transactions. The miners hash a block header in order to make the block valid. This is more effective than hashing the entire block, which can contain hundreds of transactions. 

Changing the nonce and rehashing an entire 2MB block for each trial would be far more inconvenient for a miner. This significantly differs from hashing Bitcoin's block headers, which have a constant length of 80 bytes. Block headers are wonderful for mining but also great for light clients because of their compact size. 

Understanding a Block Header

The Bitcoin blockchain is too vast to store on mobile devices like smartphones. You'd need 100GB of space if the chain had 100,000 1MB blocks. On the other hand, the block headers for those identical blocks would only take up 0.008GB, or 8MB. Devices with limited bandwidth or storage space can do some validation in this way. 

They can later verify if a transaction has been included in the given block because the Merkle root encompasses all transactions. However, this comes with a price: the user must still depend on a third party to give them the required information. On the other hand, light clients refer to a system in which users conduct no authentication at all.