Genesis Block Rule

Only blocks that add to the block chain formed by building upon the Genesis block are valid.

This rule states that blocks must be added to an unbroken chain of proof of work leading back to the genesis block, which has its block hash hard coded into the Bitcoin node client’s software. This prevents a malicious party somehow creating a new chain in order to perpetrate a malicious redirection of hashpower or economic activity, and is an important aspect of Simplified Payment Verification, allowing users to check they are using the correct chain of blocks with minimal overhead.

The genesis block is identified using its block hash which is 000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f. By ensuring all users of the network are aware of this block hash, there can be certainty around which chain of blocks is valid. If a user or node connects to a chain of blocks which leads back to a point of origin that is not the genesis block, it can know immediately that it has connected to the wrong network.