GlossaryAdvanced
Soft Fork
A protocol change that remains compatible with nodes running older software.
A soft fork tightens a blockchain's existing rules in a way that older, non-upgraded nodes still recognize as valid, even though they don't enforce the new rule themselves.
Because old nodes still accept blocks that follow the new, stricter rules, a soft fork generally doesn't split the network the way a hard fork can, as long as enough of the network adopts it. See Kaavon's "Hard Fork" glossary definition for the backward-incompatible alternative, and "Taproot" for a real, named Bitcoin upgrade activated this way.
Examples
- A soft fork might reduce the maximum allowed block size, which older nodes would still see as valid.
- Soft forks are often preferred over hard forks when a change can be made without breaking compatibility.