soft fork
A blockchain upgrade that tightens rules in a backward-compatible way.
A soft fork is a change to a blockchain’s rules that makes them stricter, but remains compatible with older software. Think of it like a store deciding to stop accepting old coins in addition to new ones—the old coins are still valid elsewhere, but the store won’t take them. Nodes (computers running the network) that haven’t updated will still recognize transactions and blocks as valid, even if they don’t fully understand the new rules.
Soft forks are less disruptive than “hard forks,” which break compatibility entirely. When you see a soft fork announced, it typically means the network is adding security measures or fixing edge cases without forcing everyone to upgrade immediately. The upgrade is optional technically, but miners and validators are expected to adopt it, making it effective in practice. Most blockchain updates are soft forks precisely because they don’t split the network into incompatible versions.
Written once as a plain-English reference, not as advice. Nothing here is a recommendation to buy or sell anything.