What Are Bitcoin Hard Forks?
In early 2009, a mysterious software developer, working under the alias Satoshi Nakamoto, released a software program that created bitcoin, the first cryptocurrency. Since then, bitcoin has gone on to gain massive appeal across the globe and inspire hundreds of other digital currencies.
Many of these cryptocurrencies employ technologies that were already inherent in Satoshi's initial program and concept. Others take the bitcoin model and adapt or attempt to improve upon it. In some cases, bitcoin has spawned variations that are based on the same underlying concept and program but that are distinct from the original. In these situations, the bitcoin blockchain has undergone a process known as forking. With forking, the blockchain itself is divided into two distinct entities.
A bitcoin hard fork refers to a radical change to the protocol of bitcoin's blockchain that effectively results in two branches, one that follows the previous protocol and one that follows the new version.
During a hard fork, software implementing bitcoin and its mining procedures is upgraded; once a user upgrades their software, that version rejects all transactions from older software, effectively creating a new branch of the blockchain.
It is through this forking process that various digital currencies with names similar to bitcoin have been created, including bitcoin cash and bitcoin gold.
Bitcoin XT was one of the first notable hard forks of bitcoin.