I understand what is hardfork in theory. Hardfork happens, when the consensus algorithm changes (if I'm wrong, correct me please). Ok, with theory everything is clear, but what about technical side of this question? How exactly hardfork occurs, how exactly chain divides? Thank you for your answers
closed as too broad by Pieter Wuille, Raghav Sood, Andrew Chow♦ Apr 9 '18 at 15:47
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A new version of the software is implemented, which uses the new rules. The old software will see the new transactions/blocks generated by this new software as invalid after the fork date, while new software will accept it, so the old software and new software will disagree on the longest valid blockchain, creating a hard fork.