It is a soft fork. https://bitcoinmagazine.com/technical/bip-8-bip-9-or-modern-soft-fork-activation-how-bitcoin-could-upgrade-next https://bitcoinmagazine.com/t

It is a soft fork. https://bitcoinmagazine.com/technical/bip-8-bip-9-or-modern-soft-fork-activation-how-bitcoin-could-upgrade-next https://bitcoinmagazine.com/technical/bip-8-bip-9-or-modern-... "The nice thing about adding or tightening rules is that anything that an upgraded node considers valid, a non-upgraded node considers valid, too." The signalling mechanism is a way for the miners to vote ahead of time whether they will follow to the new fork or not. If more than 10% of the hash power of the network does not signal that it will follow, then the fork is called off and won't happen.