What is Bitcoin's genesis block?

Detailed explanation

The genesis block is the defined starting point of the Bitcoin blockchain. Satoshi Nakamoto created it on January 3, 2009. In the network's numbering, it has block height 0. Later blocks refer to their predecessor's hash, but the genesis block's reference to a previous block is empty because no such block existed.

The block contains a newspaper headline from the same day about a possible further bank bailout in the United Kingdom. The headline provides a time reference indicating that the block data was not prepared before that edition was published. The message is also often interpreted as a comment on the financial system of the time. The text alone, however, cannot establish Satoshi's precise personal intention beyond doubt.

The genesis block is defined in the Bitcoin Core code as the main network's starting point. Its original block reward cannot be spent because of its special technical construction. For beginners, the key point is that it is neither the first block after a halving nor an emergency block. It is the one-time beginning of Bitcoin's shared block history.