Soft Fork

Soft fork is a change to blockchain protocol rules that makes the set of valid blocks or transactions more restricted.

A typical property of a soft fork is that blocks satisfying the new, stricter rules can remain acceptable under the older rule set, although nodes running older software may not independently enforce the new restrictions.

Activation

The activation method depends on the protocol. It can involve signaling by network participants, a specific block height, a time-based condition, or another defined mechanism.

A soft fork does not mean that chain divergence is impossible. If participants enforce different rules, the resulting behavior depends on the compatibility properties and consensus design of the particular network.