Genesis Block Definition

A genesis block is the very first block of a blockchain. You may also see it called Block 0 or Block 1. It starts the ledger from scratch and anchors everything that follows.

Role in blockchains

Every block usually points to the one before it using a reference to the previous block’s data. The genesis block is the exception because there is no earlier block to reference. That is why the chain begins here and grows forward from this point.\

How software treats it

Because the first block has no parent, most blockchain clients include the genesis block directly in their code. This hardcoded anchor gives all nodes a common starting point when they join the network.

Names you might see

Writers and developers sometimes call the same thing Block 0 or Block 1. Both labels refer to the very first block that kicks off the chain.

Why the first reward is different

In many networks, the initial mining reward linked to the genesis block is unspendable. This sets the block apart from normal blocks that come after it.

Bitcoin’s genesis block

Bitcoin’s best-known genesis block was created on January 3, 2009, by the pseudonymous founder Satoshi Nakamoto. It carried a coinbase reward of 50 BTC that was sent to a valid address yet remains unspent. In the block’s data, Satoshi included the headline “The Times 03/Jan/2009 Chancellor on brink of second bailout for banks.” The next block appeared days later, which sparked plenty of discussion among observers.

Starting new networks

Launching a new blockchain means defining a genesis block so all participants agree on the system’s first state. From there, the chain grows as new blocks link back to that starting point.