A soft fork is a backward-compatible protocol upgrade, which preserves compatibility with the original protocol. Even though new rules are introduced, nodes using the original software can still see blocks generated under the updated stipulations. However, they might not be able to perform functions such as block validations. New system benefits may also not be available.
Soft forks don’t oblige network participants to move to the new upgrade straight away. That means most participants can continue to operate on the network but only if more than half of them adhere to the new rules.
Most soft forks occur as an attempt to enhance security, mend problems with the protocol, launch new features, or optimize the overall performance of the blockchain, all while keeping uninterrupted operations on the original blockchain. The Segregated Witness (SegWit) activation on Bitcoin in 2017 is arguably the most commonly cited soft fork example.
