Glossary / Mining & consensus
Genesis block
Also known as Block 0.
- Definition
- The genesis block is the first block of the bitcoin chain, hard coded into the software on January 3, 2009, and the only block whose 50 coin reward can never be spent.
Every bitcoin node starts from the same hard coded block rather than downloading it, because there is nothing earlier to check it against. Its timestamp, 1231006505, resolves to January 3, 2009 at 18:15:05 UTC, and its coinbase field carries a headline from that morning's Times of London. If your software does not arrive at the same genesis, you are not on bitcoin.
How it works
The genesis block is the one block no node ever validates against a parent, so it cannot be transmitted, only agreed upon.
It lives in the source code, in the chain parameters file, alongside the equivalent starting blocks for testnet, signet and regtest. Each network gets its own, which is exactly how a node knows which network it is on: a testnet node reuses the same coinbase message but a different timestamp and nonce, producing a different hash, and the two networks can never accidentally merge. Change one byte of your genesis and you have created a private chain that no peer will talk to.
The whole block is 285 bytes and contains a single transaction, the coinbase that pays the first 50 coins. Those coins cannot be spent, and not because a rule forbids it. Bitcoin Core never inserts the genesis coinbase output into its set of unspent outputs, an artifact of how the block is loaded rather than a deliberate design, so any transaction trying to consume it names an output the network does not believe exists. Every implementation has kept the quirk, because changing it would fork the chain to no purpose.
Nothing followed it for a while. Block 1 was not mined until January 9, 2009, more than five days later, the same day the version 0.1 software was announced on the Cryptography mailing list. The gap is why the genesis block is often described as pre announcement: it existed before anyone else could have been running the code.
People still send coins to the genesis address, 1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa, as tribute. Those later payments are ordinary outputs, created by ordinary transactions, and are spendable by whoever holds that key. Only the original 50 are frozen.
Why this matters when you buy bitcoin
Sharing bitcoin's genesis block proves nothing about a coin, and several projects have sold exactly that confusion.
Bitcoin Cash split away at block 478,558 on August 1, 2017. Bitcoin SV split from Bitcoin Cash on November 15, 2018. Bitcoin Gold split at block 491,407 in October 2017. All of them contain the identical genesis block, the identical headline in the identical coinbase field, and the identical first several years of history, because a fork copies everything up to the point where it leaves. A project can therefore say, truthfully, that its chain begins on January 3, 2009, and still be a different asset with a different price, different rules, and a fraction of the security.
What separates the chains is everything after the fork point: the consensus rules each side enforces and the accumulated proof of work behind the tip. When you buy, the things that actually identify bitcoin are the ticker your platform trades, the address format your wallet produces, and the chain your node follows. None of them is the genesis block.
The second practical use is verification. When your node performs its initial sync it starts at block 0 and walks forward, checking every subsidy, every signature and every link. The genesis block is the one input to that process that comes from you rather than from the network, which is the whole reason the process means anything. Downloading your own copy of the software from the project's own release page, and checking its signature, is what makes the starting point yours.
Then there is the scam layer. "Satoshi era" coin offers, chains sold as the original bitcoin, and messages asking you to send to the genesis address to unlock a multiplier all trade on the same misunderstanding. Our scam guide covers the pattern.
The headline in the coinbase field
The genesis coinbase input carries a 69 byte push of plain text that a hex to ASCII converter will read back to you in a second.
The bytes decode to: The Times 03/Jan/2009 Chancellor on brink of second bailout for banks. That was the front page headline of The Times of London on Saturday, January 3, 2009, referring to Alistair Darling and the second UK bank rescue.
It does two jobs at once. It is a statement about why the thing was built, the only editorial content anywhere in the protocol. It is also a timestamp proof of the kind used in cryptography for decades: the block cannot have been created before the newspaper existed, which sets a hard lower bound on the chain's age that does not depend on trusting the timestamp field. Anyone claiming to have mined an earlier bitcoin chain has to explain a headline they could not have known.
Genesis block vs bitcoin whitepaper
Bitcoin has three plausible birthdays and people mix them constantly. The whitepaper was posted to the Cryptography mailing list on October 31, 2008: a nine page design document, no code, no chain. The genesis block was mined on January 3, 2009: the first state of the ledger. The version 0.1 software was released on January 9, 2009: the point at which anyone else could join. The whitepaper describes a system; the genesis block starts one.
Genesis block vs Satoshi Nakamoto
"Satoshi's coins" almost never means the genesis 50. Sergio Demian Lerner's analysis of nonce patterns in early blocks, known as the Patoshi pattern, attributes roughly 1.1 million coins to a single miner during 2009, and those are ordinary spendable outputs sitting in ordinary addresses. The genesis reward is separate and is not spendable by anyone, Satoshi included. So when a headline reports that a dormant early wallet has moved, it is never the genesis block, and it never can be.