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What is a soft fork?
A soft fork is a change to a blockchain's rules that makes them stricter, so blocks following the new rules are still accepted by nodes that have not upgraded. In Bitcoin it can take effect without splitting the chain, provided miners with most of the hashing power enforce the new rules.
What it means for you
Your coins and older wallet software keep working after a soft fork, but an old node no longer checks every new rule and relies on the upgraded majority for those checks. Features a soft fork adds, such as new address types, work only once your wallet supports them.
How it works
Consensus rules decide which blocks are valid. A soft fork tightens them: upgraded nodes reject some blocks old nodes would accept, while blocks valid under the new rules stay valid under the old. If upgraded nodes control a majority of hash rate, they keep one chain that non-upgraded nodes also follow. Activation can be miner-signalled (a miner-activated soft fork, typically needing 75% or 95% of hash rate to signal readiness) or fixed to a preset time or block height (user-activated). SegWit worked this way: old nodes treat its outputs as anyone-can-spend.
Sources: Bitcoin Developer Guide: Block Chain (consensus rule changes), BIP-141: Segregated Witness (backward compatibility) · checked 4 October 2026
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