24
5
When people talk about possible changes to how Bitcoin works they sometimes say a particular change would require a hard fork. What does that mean? Can a hard fork cause problems?
What is a hard fork?
Answers
21
Simply put, a so-called hard fork is a change of the Bitcoin protocol that is not backwards-compatible; i.e., older client versions would not accept blocks created by the updated client, considering them invalid. Obviously, this can create a blockchain fork when nodes running the new version create a separate blockchain incompatible with the older software.
For potential future changes that would require a hard fork, see the associated wiki page.
Should 'hard fork' not be constrained to Bitcoin protocol, and strictly define a condition in a blockchain network where node consensus diverges permanently. – Goddard – 2016-11-28T16:09:54.637
What do you mean? The answer of BinaryMage mentions "is a change of the Bitcoin protocol". – Murch – 2016-11-28T16:17:50.740
He meant limiting the definition to Bitcoin is unnecessarily restrictive. Ethereum has had hard forks too, and @BinaryMage's description of what a hard fork is would work equally well there, except for the fact that Ethereum doesn't use the Bitcoin protocol. – Nik Bougalis – 2016-11-28T16:33:19.373
1I think you mean HF is not forward-compatible. It is BWC in the sense that "the new understands the old" which is the common definition in most dictionaries. – jiggunjer – 2017-10-26T09:46:05.297
3
related: What is a soft fork?
– morsecoder – 2015-01-30T23:02:28.077Will Hard fork affect Bitcoin value to decrease? I mean due to Blockchain split – Salvator NKUNZIMANA – 2017-03-27T19:40:53.750