Bitcoin is open source, so anyone can copy the code and start a new coin. A fork goes one step further: it keeps Bitcoin's history and splits off at a chosen block.
Bitcoin Cash (2017)
Bitcoin Cash diverged after block 478,558 on 1 August 2017 with a larger block size limit. Everyone who held bitcoin at the split also received the same amount of BCH.
Bitcoin SV (2018)
In November 2018 Bitcoin Cash itself split. One side, Bitcoin SV ("Satoshi Vision"), was championed by Craig Wright – whom the UK High Court ruled in 2024 is not Satoshi and who forged documents.
Others
Many other "Bitcoin" forks appeared in 2017–2018; most have little use today.
Why the original wins
- Names do not decide; users, nodes, wallets and exchanges choosing which rules to follow do.
- The chain with the strongest security and widest acceptance keeps the network effect.
- The original chain has remained the one most widely called "Bitcoin".
Forks are a feature: anyone who disagrees can leave without forcing everyone else to change.