Genesis Block

The genesis block is the first block ever created on a blockchain — block number zero. It is the root of the chain that every subsequent block links back to.

How it works

Unlike every block after it, the genesis block has no previous block to reference, so it is hard-coded directly into the network’s software. Each later block points back to the one before it, forming an unbroken chain that ultimately traces to the genesis block. This shared starting point is something all nodes agree on by definition.

Why it matters

The genesis block anchors the entire history of a network and is often symbolically important. Bitcoin’s genesis block famously embedded a newspaper headline in its data, a permanent timestamp marking the moment the network began.

Example

Tracing any Bitcoin transaction back through the chain eventually leads to the 2009 genesis block.