Bitcoin Core , descendant of the original Bitcoin software launched by Satoshi Nakamoto in 2009, has always been Bitcoin’s reference client. The implementation, formerly known as Bitcoin QT, proposes standards for the Bitcoin protocol itself. But these standards are not binding. Based on open source software, anyone can take the code, modify it as they see fit, and offer the adjusted version to the world.
This was recently highlighted by the launch of Bitcoin Classic and Bitcoin Unlimited , and Bitcoin XT before that. But these implementations did something that hadn’t been attempted before, at least not in serious form. They forked the software such that it could become incompatible with Bitcoin’s existing consensus rules, essentially proposing that users switch to a network that is not backwards-compatible. Bitcoin Classic, Bitcoin Unlimited and Bitcoin XT are not just software forks, they are consensus forks .
Forking Bitcoin Core’s software itself, however, has been done several times before without raising consensus issues. At least three prominent developers, all of whom contribute to Bitcoin Core, maintain their own forks, adjusted to fit their vision and preferred use cases for Bitcoin. Because none of these break with existing consensus rules, they are fully compatible with the current Bitcoin network.
Bitcoin RBF (by Peter Todd)
“ Bitcoin RBF ” (it has no official name) is a Bitcoin Core fork maintained by Peter Todd, and was launched in early 2014. It’s a straight copy of Bitcoin Core, except for its memory pool (“mempool”) policy: the rules that decide which unconfirmed transactions are accepted and rejected.
Most Bitcoin nodes currently apply a “first seen” mempool policy, which means they reject incoming transactions if they conflict with earlier unconfirmed transactions. And Bitcoin Core recently introduced “opt-in replace-by-fee,” which replaces a transaction with a conflicting transaction that includes a higher fee […]
