Genesis Block
The genesis block is the first block of a blockchain. Bitcoin's genesis block, also called block 0, was created by Satoshi Nakamoto on 3 January 2009 and is the starting point every later block builds on.
What makes it special
Every block in a blockchain contains the hash, a kind of digital fingerprint, of the block before it. That link is what chains the blocks together. The genesis block is the only block with no predecessor, so it is written directly into the Bitcoin software rather than being mined and accepted from the network like later blocks.
The term is general: every blockchain has its own genesis block. Ethereum's, for example, was created in July 2015. When people say the genesis block without further context, they usually mean Bitcoin's.
The newspaper headline
Satoshi embedded a short text in the genesis block: The Times 03/Jan/2009 Chancellor on brink of second bailout for banks. It quotes the front page of the British newspaper The Times from that day. The line proves the block was not created before that date, and it is widely read as a comment on the bank bailouts of the 2008 financial crisis that Bitcoin was meant to offer an alternative to.
The 50 bitcoin that cannot be spent
The genesis block carries a block reward of 50 BTC, but because of how the original code handles this block, those coins cannot be spent. Over the years people have sent small amounts to the genesis address as a tribute, and those are stuck as well. Whether this was deliberate or a quirk has never been confirmed.
Why it matters
The genesis block anchors the whole chain. Any node can start from it and verify every block since, checking that the full history follows the rules. It is also a reminder that Bitcoin's history can be audited from day one by anyone.
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Frequently asked questions
When was Bitcoin's genesis block created?
Its timestamp is 3 January 2009. The next block, block 1, followed on 9 January 2009, around when the software was released publicly.
Who mined the genesis block?
Satoshi Nakamoto, Bitcoin's pseudonymous creator.
Can the coins in the genesis block be spent?
No. The 50 BTC reward is not spendable because of how the original software treats the genesis block, and coins sent to that address later are also effectively locked.
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