What is Block Header

The block header is the part of a block in a blockchain that provides a synopsis of the block. Among other metadata, the block header contains the hash of the previous block, the block’s Merkle root, block’s nonce, and a timestamp.

Block headers are useful because they allow to decrease the time and energy consumed to validate blocks. During mining, miners try numerous nonce values iteratively before finding the correct solution. Hashing block headers is more feasible than hashing all the thousands of transactions included in a block.