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Consensus and rule changes

9 min read

Bitcoin's rules can change, but only by proposal, discussion and voluntary adoption by node operators, never by a single party's decree.

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A Bitcoin Improvement Proposal (BIP) is a written, publicly reviewed document describing a proposed change, it can range from a minor API convention to a fundamental consensus rule. Writing a BIP does not make it a rule; it becomes one only if node operators and, in practice, the broader ecosystem choose to run software that enforces it.

Rule changes are categorised by compatibility. A soft fork tightens the rules: blocks that were valid before might now be rejected, but blocks that follow the new, stricter rules are still valid under the old rules too, so upgraded and non-upgraded nodes can usually coexist on the same chain. A hard fork loosens or changes the rules such that some blocks valid under the new rules would be rejected by old nodes, which requires every participating node to upgrade or risk following a separate, incompatible chain.

SegWit (2017) and Taproot (2021) were both deployed as soft forks, activated once a sufficient share of mined blocks signalled readiness over a defined period. This mechanism, miners signalling, but ultimately node operators enforcing, means widespread rule changes require broad, largely voluntary coordination rather than a vote by a governing body, which is also why contentious changes can be slow or can fail to gain the support needed to activate.

Explain more simply

Bitcoin's software can be improved, but no single person or company can force a change onto everyone else. Every node operator chooses which software version to run.

Proposals go through a public process called a BIP (Bitcoin Improvement Proposal), get discussed for a long time, and only take effect if enough of the network actually adopts them.

Real-world analogy

Changing a Bitcoin rule is like changing the rules of a sport that millions already play: a governing body can publish a new rulebook, but the change only matters if leagues, referees and players actually adopt it, otherwise people just keep playing by the old rules.

Key facts

  • A BIP is a written proposal; it only becomes an active rule if node operators adopt software enforcing it.
  • A soft fork tightens rules and is backward-compatible with old nodes; a hard fork changes rules incompatibly and requires universal upgrade.
  • SegWit and Taproot were both activated as soft forks after sufficient signalled readiness.

Common misconception

“Bitcoin developers or a foundation can push out a rule change and everyone must accept it.”

Developers can write and propose code, but they cannot force anyone to run it. A rule change only takes effect if node operators across the network voluntarily choose to adopt software enforcing it, which is why contentious proposals can stall indefinitely.[4]

Go deeper

The 2017 'UASF' (User-Activated Soft Fork) movement around SegWit demonstrated that node operators and economic users, not just miners, can force activation pressure: by committing to enforce new rules on a fixed future date regardless of miner signalling, UASF advocates threatened to split off any miners who continued producing blocks under the old rules, which shifted the practical incentive for miners to signal readiness.

A change to the 21 million supply cap would require a hard fork, since it alters what counts as valid issuance; because raising it would require essentially every economically significant node, exchange and business to voluntarily adopt software that breaks compatibility with the existing chain, there is no realistic mechanism, social or technical, by which a small group could impose it on the network.

Quick check

Answer every question correctly (100%) to complete this lesson.

  1. 1.What is the key difference between a soft fork and a hard fork?

    What is the key difference between a soft fork and a hard fork?

  2. 2.Why can't a small group unilaterally raise the 21 million supply cap?

    Why can't a small group unilaterally raise the 21 million supply cap?

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Extra exam questions

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16 questions

Quick check

Answer every question correctly (100%) to complete this lesson.

  1. 1.What is a soft fork?

    What is a soft fork?

  2. 2.What is a hard fork?

    What is a hard fork?

  3. 3.Was SegWit activated as a soft fork or a hard fork?

    Was SegWit activated as a soft fork or a hard fork?

  4. 4.Was Taproot activated as a soft fork or a hard fork?

    Was Taproot activated as a soft fork or a hard fork?

  5. 5.What is a BIP?

    What is a BIP?

  6. 6.Who has the final authority to force a rule change onto the Bitcoin network?

    Who has the final authority to force a rule change onto the Bitcoin network?

  7. 7.Why do full nodes matter for enforcing consensus rules?

    Why do full nodes matter for enforcing consensus rules?

  8. 8.What does it mean if a proposed hard fork lacks near-universal node/user adoption?

    What does it mean if a proposed hard fork lacks near-universal node/user adoption?

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Sources