What is Soft fork?
A rule change that tightens what is valid, so old nodes still accept new blocks.
Because the new rules are a subset of the old, non-upgraded nodes continue to follow the chain. SegWit and Taproot were both deployed this way.
Soft forks are the preferred upgrade path precisely because they do not force everyone to move at once.
Related terms
Hard fork
A rule change that loosens what is valid, so old nodes reject the new blocks and the chain splits unless…
NetworkConsensus rules
The validity conditions every node enforces: issuance schedule, signature validity, block weight, and…
NetworkSegWit
A 2017 soft fork that moved signature data into a separate witness structure, fixing transaction malleability…
NetworkTaproot
A 2021 soft fork adding Schnorr signatures and a scheme that makes complex spending conditions look like…
This definition is part of the Bitcoin Logical glossary. For the fuller explanation, start with Learn, or see the live numbers on The Bitcoin Signal.