Soft Fork Vs Hard Fork

A soft fork is a backward-compatible protocol upgrade where only previously invalid blocks become valid, meaning non-upgraded nodes can still process transactions. A hard fork is a non-backward-compatible upgrade that changes the protocol rules so significantly that old nodes cannot validate new blocks, effectively creating a permanent divergence in the blockchain.

In a soft fork, the network remains unified because the new rules are a subset of the old rules. In a hard fork, the network splits into two separate chains unless all participants upgrade to the new software.

Soft forks are generally easier to coordinate but more constrained in design. Hard forks allow for major structural changes but carry the risk of community fragmentation.

Both mechanisms are essential for evolving decentralized consensus protocols.