Block size wars
A sourced map of Bitcoin's 2015 to 2017 capacity fight: XT, Classic, Unlimited, SegWit, UASF, the Hong Kong and New York Agreements, SegWit2x's cancellation, and the Bitcoin Cash fork. Podcast guests who lived through it are linked with Listen cues.
Read this first. Positions below are historical snapshots with sources. People change their minds. Where a switch is documented, it is labelled with a date and a citation. This page does not settle who was right.
Bitcoin Forks, Described by Dorks · Bitcoin history timeline · Satoshi-era timeline
Two camps
Pressed for hard-fork capacity increases via Bitcoin XT, Classic, Unlimited and later Bitcoin Cash. Argued fees and confirmation delays were choking peer-to-peer cash.
Pressed for SegWit soft-fork upgrades, Lightning and cautious hard forks. Argued large blocks threatened decentralisation of full nodes.
Clients and proposals
- 2015 Larger blocks
Bitcoin XT
Mike Hearn and Gavin Andresen promoted XT with BIP101-style larger blocks. Hashpower and node signalling never reached a clean activation; XT became the opening salvo of the war.
Often associated with: Mike Hearn; Gavin Andresen
Sources: Wikipedia: Bitcoin scalability problem · Hearn farewell (2016)
- 2016 Larger blocks
Bitcoin Classic
Classic sought a more modest hard-fork bump (often discussed as 2 MB) after XT stalled. It competed with Unlimited for big-block mindshare.
Sources: Wikipedia: Bitcoin scalability problem · Forks described by dorks
- 2016–2017 Larger blocks
Bitcoin Unlimited
Unlimited let miners set emergent block size limits. It attracted mining pools before the August 2017 split and later fed into Bitcoin Cash culture.
Sources: Wikipedia: Bitcoin Unlimited
- 2015–2017 SegWit path
Bitcoin Core + SegWit
Core maintainers and many node operators backed SegWit (BIP141) as a soft fork, paired with Lightning research, rather than a large immediate hard fork.
Often associated with: Pieter Wuille (SegWit design); many Bitcoin Core contributors
Sources: BIP 141 · Wikipedia: SegWit
- 2017 Larger blocks
SegWit2x (NYA)
Industry letter agreeing to activate SegWit then hard-fork to ~2 MB. Cancelled in November 2017 after failing to hold consensus.
Often associated with: NYA company signatories (see list)
Sources: DCG Medium: Bitcoin Scaling Agreement at Consensus 2017
War timeline
- Larger blocks
Bitcoin XT opens the war
XT with larger-block signalling makes capacity a political client fight, not only a mailing-list argument.
Sources: Wikipedia: Bitcoin scalability problem
Charlie Shrem Play on click, quiet fade · 2:41
- Larger blocks
Mike Hearn leaves Bitcoin
Hearn publishes that the experiment has failed after XT and capacity politics. A documented exit from the big-block developer camp's most visible advocate.
-
Hong Kong Agreement
Miners and developers meet aiming at SegWit plus a later hard-fork path. The political deal does not hold cleanly into 2017.
Sources: Contemporary HK Agreement coverage / SegWit wiki context
- Larger blocks
Classic and Unlimited campaigns
Competing big-block clients keep pressure on Core while SegWit code matures.
Sources: Wikipedia: Bitcoin Unlimited
- Larger blocks
New York Agreement published
Digital Currency Group publishes the Consensus 2017 scaling letter: SegWit at 80% bit-4 signalling, then a 2 MB hard fork within six months.
Sources: DCG Medium: Bitcoin Scaling Agreement at Consensus 2017
Charlie Shrem Play on click, quiet fade · 2:41
- SegWit path
UASF / BIP148 organises
User-activated soft fork organising threatens to activate SegWit from the economic-node side if miners stall.
Sources: BIP 148
Amir Taaki Play on click, quiet fade · 32:00
- Larger blocks
Bitcoin Cash chain split
A hard fork creates Bitcoin Cash with larger blocks. Many big-block advocates move ongoing on-chain cash arguments to BCH.
Sources: Wikipedia: Bitcoin Cash · Forks described by dorks (BCH)
Calin Culianu & Steve Thurmond Play on click, quiet fade · 1:09
- SegWit path
SegWit activates on Bitcoin
SegWit activates on the Bitcoin chain, enabling Lightning-friendly formats while the NYA hard fork is still pending.
Sources: Wikipedia: SegWit
-
SegWit2x cancelled
SegWit2x leaders abandon the November hard fork. The NYA chain-split threat ends without a second BTC UTXO split.
Sources: DCG NYA letter (context) · Forks described by dorks (SegWit2x)
John Carvalho Play on click, quiet fade · 58:32
New York Agreement signatories
Copied from the published DCG letter's "Supporters as of May 25" list. The letter states BitGo was erroneously included in an earlier draft and corrected; BitGo is omitted here. Signing a company letter is not the same as every employee agreeing, and some signatories later opposed SegWit2x or supported BCH instead.
Primary source: DCG Medium: Bitcoin Scaling Agreement at Consensus 2017 (list as of 25 May 2017) · dated 23 May 2017 · 56 names listed
- 1Hash (China)
- Abra (United States)
- ANX (Hong Kong)
- Bitangel.com / Chandler Guo (China)
- BitClub Network (Hong Kong)
- Bitcoin.com (St. Kitts & Nevis)
- Bitex (Argentina)
- bitFlyer (Japan)
- Bitfury (United States)
- Bitmain (China)
- BitPay (United States)
- BitPesa (Kenya)
- BitOasis (United Arab Emirates)
- Bitso (Mexico)
- Bitwala (Germany)
- Bixin.com (China)
- Blockchain (UK)
- Bloq (United States)
- btc.com (China)
- BTCC (China)
- BTC.TOP (China)
- BTER.com (China)
- Circle (United States)
- Civic (United States)
- Coinbase (United States)
- Coins.ph (Philippines)
- CryptoFacilities (UK)
- Decentral (Canada)
- Digital Currency Group (United States)
- F2Pool (China)
- Filament (United States)
- Gavin Andresen (United States)
- Genesis Global Trading (United States)
- Genesis Mining (Hong Kong)
- GoCoin (Isle of Man)
- Grayscale Investments (United States)
- Guy Corem (Israel)
- Jaxx (Canada)
- Korbit (South Korea)
- Luno (Singapore)
- MONI (Finland)
- Netki (United States)
- OB1 (United States)
- Purse (United States)
- Ripio (Argentina)
- Safello (Sweden)
- SFOX (United States)
- ShapeShift (Switzerland)
- surBTC (Chile)
- Unocoin (India)
- Vaultoro (Germany)
- Veem (United States)
- ViaBTC (China)
- Wayniloans (Argentina)
- Xapo (United States)
- Yours (United States)
Documented side changes
Only switches with a published source are listed. Approximate personal dates are labelled uncertain.
- 14 January 2016
Mike Hearn
From: Bitcoin XT / larger blocks advocate and Core contributor
To: Public exit from Bitcoin (Jan 2016)Documented in his own farewell essay; not a move to another coin so much as a withdrawal.
Sources: Hearn farewell essay
- 1 January 2021 · date approximate
Bobby Lee
From: Big-block camp (his own description)
To: Returned to supporting Bitcoin (BTC) as the monetary networkOn Bitcoin Takeover he describes coming back from the big-blocker camp. Exact calendar date of his personal shift is not pinned beyond the interview; treat the year as approximate.
Sources: BTK S5 E1 Bobby Lee chapter: comeback from the big blocker camp
- 1 August 2017
Roger Ver
From: Early Bitcoin investor/advocate
To: Public Bitcoin Cash advocate after the 2017 splitWidely documented public advocacy for BCH after August 2017; see his interviews on this site.
Sources: Guest hub: Roger Ver · Wikipedia: Roger Ver
