Genesis Block

The genesis block is the very first block of a blockchain, block number zero, hard-coded into the network's software rather than mined or validated in the usual way. Every later block points back to it through the chain of parent hashes, so it anchors the entire ledger; nodes that disagree about the genesis block are simply on different networks. Genesis blocks often set initial parameters such as the starting difficulty and any pre-allocated balances, and developers sometimes embed a message in them — Bitcoin's famously contains a newspaper headline. When a project launches a new chain or a testnet, creating a genesis file with agreed parameters is the first step every node must share.