Bitcoin forks & civil wars

Blocksize feud and camps

Scaling visions collide

From 2015 onward, Bitcoin argued over how to scale: increase block size (cheaper on-chain transactions) or keep blocks small and push activity to layers like Lightning. “Big blockers” wanted fast, cheap on-chain payments; “small blockers” prioritized decentralization and verifiability by keeping node requirements low.

The debate was technical and cultural: is Bitcoin digital cash for daily use or a base layer for settlement and savings? Mailing lists, Reddit, and conferences became battlegrounds.

SegWit enters

Segregated Witness (SegWit) proposed a soft fork to fix transaction malleability and increase effective block capacity by moving witness data. It set the stage for Lightning. Many supported it; some saw it as insufficient without a hard block size bump. Pieter Wuille’s SegWit explainer ↗ became canonical.

Business/ miner pushback

Large miners and some businesses wanted a block size hard fork. They argued higher throughput would keep users from leaving for altcoins. Concerns about miner power and centralization colored the debate—who gets to set Bitcoin’s rules?

Fork attempts and aftermath

New York Agreement (SegWit2x)

In 2017, some miners and companies signed the NYA, agreeing to activate SegWit and later hard fork to 2MB blocks (SegWit2x). The deal lacked broad node consensus. Code was written; a fork date was set. Many users and developers opposed the “closed-door” governance. The signed NYA text ↗ is still online.

User-Activated Soft Fork (UASF)

Grassroots users proposed BIP148, a UASF: nodes would reject non-SegWit blocks after Aug 1, 2017. This pressured miners to signal SegWit to avoid chain splits. It worked—miners activated SegWit, showing economic nodes could steer outcomes. The BIP148 spec ↗ reads like a grassroots manifesto.

Bitcoin Cash splits off

On Aug 1, 2017, Bitcoin Cash forked with 8MB blocks and no SegWit. BCH pitched itself as “peer-to-peer cash” with cheap on-chain fees. Exchanges credited users with BCH balances; hashpower and community split. Later, BCH itself forked (BSV), proving forks can fork again. The BCH roadmap ↗ framed its vision.

SegWit2x collapse

The planned 2MB hard fork for November 2017 was canceled days before activation due to lack of consensus and fear of chain chaos. Bitcoin continued with SegWit and the existing block size, while Lightning development accelerated. The cancellation email (Mike Belshe’s note ↗) marked the end of SegWit2x.

Lessons and lasting norms

Nodes matter

The UASF episode underscored that full nodes, not just miners or companies, shape consensus. Economic majority (exchanges, wallets, users) can resist miner/business deals if they don’t run the code.

Governance is social

Bitcoin has no formal voting. Rough consensus emerges through code, signaling, and social legitimacy. The blocksize war made clear that public debate and opt-in upgrades are the governance process; backroom agreements can fail spectacularly.

Forks are freedom and cost

Forks let dissenters try alternatives, but sustaining economic and developer momentum is hard. BCH and BSV communities learned that liquidity, tooling, and branding matter as much as block size. Bitcoin’s main chain reinforced its “ossification” norm—change slowly, if at all.

Layered scaling wins mindshare

SegWit paved the way for Lightning and taproot upgrades. The war cemented the idea that Bitcoin would scale in layers, preserving small node requirements. That philosophy shapes current discussions about covenants, ordinals congestion, and future soft forks.