Soft fork

A fork changes the rules every nodeGlossaryNodeA computer that runs Bitcoin software and exchanges transactions and blocks with other nodes. Together, the nodes form the Bitcoin network; full nodes check every rule themselves.On the learning path: Stage 1 · Step 3 – How does Bitcoin work? →In the glossary →× uses to check blocks. In a soft fork, they become stricter: what was allowed before is now forbidden or tied to conditions. The counterpart is the hard forkGlossaryHard forkA change to the consensus rules that allows previously invalid blocks. Old nodes reject such blocks; if not everyone goes along, two permanently separate chains emerge – and with them a new, separate currency.In the glossary →×.

Why old nodes aren’t left behind

If you follow stricter house rules, you don’t break the old ones either: blocks that follow the new rules are also valid under the old ones. Nodes that haven’t been updated therefore keep accepting them. The chain stays together as long as the majority of the computing power enforces the new rules.^[1] Well-known soft forks are SegWitGlossarySegWit (Segregated Witness)A 2017 soft fork that treats signature data (the ‘witness’) separately. It fixed transaction malleability, increased block capacity and makes payments with modern addresses (bc1q…) cheaper.In the glossary →× and TaprootGlossaryTaprootA soft fork from November 2021 that introduced Schnorr signatures and more flexible spending conditions. Complex arrangements such as multisig can look like a simple payment. Taproot addresses start with bc1p.In the glossary →×.

How a soft fork is activated

It is proposed as a BIPGlossaryBIP (Bitcoin Improvement Proposal)A publicly documented proposal for Bitcoin – for example for new rules, standards or processes. A BIP is not a decision: whether it gets used is up to users, wallets and node operators themselves.In the glossary →×. Miners often signal approval in their blocks: for Taproot, 90% of the blocks in a period of 2,016 blocks had to signal, and Taproot took effect at block 709,632 on 14 November 2021.^[2],[3] In a user-activated soft fork (UASF), by contrast, the nodes enforce the new rules from a fixed date.

Where the limits lie

If only a minority enforces stricter rules, the chain splits anyway. That happened in August 2026 with BIP-110: around eight hours after the split, the breakaway chain had two blocks and the main chain was 48 blocks ahead.^[4] Background and both points of view: Forks & controversies.