Overview
In a soft fork, the new rules are more restrictive than the old ones. Old nodes will still see new blocks as valid, but new nodes will reject blocks that don't follow the new rules. This allows for a smoother transition without splitting the chain.
Key Example
SegWit (Segregated Witness) on Bitcoin was a soft fork that changed how data was stored in blocks to increase capacity and fix transaction malleability.
Requirements
A soft fork typically requires a majority of the network's hash rate or stake to signal support before it is activated.