In this episode of Bitcoin, Explained, hosts Aaron van Wirdum and Sjors Provoost discuss a recent blog post by James Lopp titled, “Has Bitcoin Ever Hard Forked”? Hard forks are generally defined as Bitcoin protocol upgrades that remove or loosen rules, making these types of upgrades backwards-incompatible. Aaron and Sjors explain, however, that Lopp in his blog post argues that this definition isn’t very precise and suggests the term should only apply if the rule change was actually utilized. In addition, hard forks can be categorized into explicit hard forks, where the rule change was an intentional hard fork, and implicit hard forks, where the rule change wasn’t originally intended to be a hard fork at all but turned out to be one anyways.
In the second half of the podcast, Aaron and Sjors break down the seven hard forks in Bitcoin’s history that Lopp was able to find, of which five were never utilized (and should therefore arguably not be considered hard forks at all), one was explicit, and one was implicit.
Finally, Aaron and Sjors briefly discuss (a) future hard fork(s) that need(s) to happen, and what kind of philosophy around deploying hard forks might make sense for Bitcoin.