Forks & Chain Divergence

Bitcoin Cash, Bitcoin SV, and soft forks — the major schisms in Bitcoin's history and the philosophical battles over "immutability."

3 min readLast updated: August 15, 2026

Key points

Forks come in two forms — backward-compatible soft forks and chain-splitting hard forks — and the 2015–2017 Block Size War produced major hard forks like Bitcoin Cash and Bitcoin SV. This history demonstrated that ultimate decision-making power rests with the consensus of node operators, not miners or corporations.

Hard Fork vs. Soft Fork

A fork is a protocol change — branching from the existing network to new rules.
Soft fork: new validity rules are a subset of existing ones. Nodes that don't implement the new rules remain compatible with nodes that do. Backward-compatible.
Hard fork: new validity rules are incompatible with existing ones. Nodes on each side recognize different chains. No backward compatibility — inevitably producing two chains.
Bitcoin conservatively prefers soft forks. SegWit (2017) and Taproot (2021) were both soft forks. Hard forks necessarily cause splits, so they're avoided unless there's total community consensus.
UASF (User Activated Soft Fork) — practiced during SegWit 2017 — activates based on node operator (user) will rather than miner signaling.

The Block Size War (2015–2017)

The fiercest internal debate in Bitcoin history. How to solve the 1MB block size limit split the community in two.
"Big Blockers": simply expand block size (hard fork). Main advocates: Roger Ver, Jihan Wu (Bitmain). Multiple expansion proposals surfaced: BIP 100/101/109/148.
"Small Blockers": scale via SegWit + Lightning Network etc. Mainstream in the Core developer community. BIP 141 SegWit was this camp's core proposal.
New York Agreement (May 2017): a compromise signed by major companies and miners: "SegWit + 2MB hard fork." The 2MB fork portion was later abandoned; only SegWit activated.
August 1, 2017: BIP 148's "enforced soft fork" (UASF) activated, formally introducing SegWit. Same day, big blockers split off Bitcoin Cash (BCH) via hard fork.

Bitcoin Cash (BCH, August 1, 2017)

Bitcoin's first major hard fork. Expanded block size to 8MB (later 32MB). Emphasized on-chain payment practicality.
Roger Ver ("Bitcoin Jesus") led powerful marketing. At one point it gained significant support in the US and Asia as "the true Bitcoin successor."
November 2018: BCH further split internally. Craig Wright (self-proclaimed Satoshi Nakamoto) and Calvin Ayre's Bitcoin SV (BSV) branched off from Bitcoin Cash ABC.
November 2020: BCH further branched into eCash (XEC) — including a re-denomination splitting 1 BCH token into 1,000,000 XEC.
As of 2026, BCH market cap is less than 1% of Bitcoin's. Bitcoin decisively won the "brand battle."

Bitcoin SV (BSV, November 2018)

Craig Wright forked from BCH under the "Satoshi Vision" banner (claiming Satoshi's original vision). Removed block size limits entirely.
Wright's persistent claim of being Satoshi Nakamoto fueled fierce controversy. In 2024, the UK High Court ruled Wright is NOT Satoshi.
Major exchange delistings: in 2019, Binance, Kraken, ShapeShift, and others delisted BSV (in response to Wright's legal threats against individuals).
2021: BSV suffered 51% attacks (multiple block reorganizations), exposing security vulnerabilities.
As of 2026, BSV market cap has further diminished — recorded in history as the archetypal "failed fork."

Major Soft Fork History

BIP 16 P2SH (2012): "Pay to Script Hash." Allows hiding scripts (like multisig) behind an address.
BIP 66 Strict DER (2015): Strict signature format. Improved cryptographic robustness.
BIP 68/112/113 CSV (2015): Relative TimeLocks. The foundation for Lightning Network's time-locking.
BIP 141 SegWit (2017): Segregated Witness. Solved transaction malleability and enabled Lightning Network.
BIP 340/341/342 Taproot (2021): Schnorr signatures, MAST, Tapscript. Privacy improvements and the foundation for Ordinals.

"What is Bitcoin?" — Governance Philosophy

The Block Size War crystallized the fundamental question: "who governs Bitcoin?"
Candidates: developers (Core contributors), miners, exchanges, large holders, regular users (node operators), corporations — which is the real decision-maker?
The conclusion: "the consensus of node operators" holds decisive power. No matter how many miners agree, if full nodes don't accept it, the result is merely a split-off chain.
This aligns with Bitcoin's core principles of "permissionless" and "censorship-resistant" operation.
The UASF (User Activated Soft Fork) concept is the practical implementation of "users are the network's guardians."

Future Fork Outlook

Soft fork candidates: OP_CAT (re-enablement), OP_CHECKTEMPLATEVERIFY (BIP 119), various CAT/Covenants proposals are under discussion. All controversial.
Quantum resistance: a soft fork introducing post-quantum signatures for Bitcoin. Discussion peaks expected around 2027-2030.
Hard forks: no serious attempts to claim "the true Bitcoin" via hard fork since 2017. The market grew fork-weary, and the community dismisses new forks after Bitcoin's victory.
"Bitcoin is Bitcoin" — this simple truth, engraved into the community after a decade of debate, demonstrates the strength of network effects.

Forks & Chain Divergence

Hard Fork vs. Soft Fork

The Block Size War (2015–2017)

Bitcoin Cash (BCH, August 1, 2017)

Bitcoin SV (BSV, November 2018)

Major Soft Fork History

"What is Bitcoin?" — Governance Philosophy

Future Fork Outlook

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