What is the Genesis Block?

Bitcoin’s Genesis Block, or block 0, starts the mainnet blockchain, the chain for Bitcoin’s primary transaction history. Each later block links to the one before it using that block’s cryptographic hash, a fixed-length value calculated from its data. Because no block comes before it, the Genesis Block gives the chain its starting point.

Its transaction specifies a 50 BTC mining reward, and the block contains a newspaper headline. Bitcoin Core treats the reward output, the part of the transaction that assigns the reward, as unspendable.

How the Genesis Block anchors Bitcoin

Bitcoin nodes, computers that check the blockchain, verify that each block links to the one before it. The Genesis Block starts that sequence: its previous-block hash is null, and later blocks trace their history back to it. Without this starting point, nodes would have no shared block to begin checking Bitcoin’s mainnet history.

The Genesis Block’s hash is:

000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f

Its block height is 0. Height counts a block’s position from the start of the chain, so the first block is numbered zero.

What the Genesis Block contains

Bitcoin’s Genesis Block contains one coinbase transaction. A coinbase transaction is the special transaction that records a miner’s block reward. The Genesis Block’s transaction specifies a reward of 50 BTC.

No one can spend the 50 BTC reward from a wallet. Bitcoin Core’s source code says the original Genesis Block output was never added to the database that tracks transaction outputs people can spend. The 50 BTC figure describes the reward specified in the transaction, not spendable funds.

The block header includes a timestamp of January 3, 2009, at 18:15:05 UTC. The timestamp alone does not verify the exact real-world time the block was created.

The headline in Bitcoin’s Genesis Block

The coinbase transaction contains this text:

The Times 03/Jan/2009 Chancellor on brink of second bailout for banks

The wording refers to a Times headline about a second bank bailout. Its presence in the block is verifiable. The headline alone does not establish why it was included or prove a specific political motive.

The headline also places the block’s creation in a recognizable historical context. Bitcoin’s white paper proposed electronic payments between users and a proof-of-work chain to record the order of transactions. This context does not settle why the headline was included.

Which Genesis Block?

“Genesis Block” can mean the first block in any blockchain. Here, it means the first block of Bitcoin mainnet, the network used for Bitcoin’s primary transaction history. Other Bitcoin networks, including test networks, have their own Genesis Blocks and different block data.