List of bitcoin forks#Taproot

The following are forks of the software client for the bitcoin network:

; Bitcoin XT: A fork initiated by Mike Hearn. The current reference implementation for bitcoin contains a computational bottleneck.{{Cite news |url=http://www.newyorker.com/business/currency/inside-the-fight-over-bitcoins-future |title=Inside the Fight Over Bitcoin's Future |author=Maria Bustillos |access-date=7 January 2017 |date=25 August 2015 |newspaper=The New Yorker |publisher=Conde Naste }} The actual fork was preceded by Mike Hearn publishing a Bitcoin Improvement Proposal (BIP 64) on June 10, 2014, calling for the addition of "a small P2P protocol extension that performs UTXO lookups given a set of outpoints."{{cite web|url=https://github.com/bitcoin/bips/blob/master/bip-0064.mediawiki|title=bips/bip-0064.mediawiki at master · bitcoin/bips · GitHub|work=GitHub}} On December 27, 2014 Hearn released version 0.10 of the forked client XT, with the BIP 64 changes.{{cite web|url=https://github.com/bitcoinxt/bitcoinxt/releases/tag/v0.10|title=bitcoinxt/bitcoinxt|website=GitHub}} It achieved significant attention within the bitcoin community in mid-2015 amid a contentious debate among core developers over increasing the block size cap.{{cite news|url=https://www.theguardian.com/technology/2015/aug/17/bitcoin-xt-alternative-cryptocurrency-chief-scientist|title=Bitcoin's forked: chief scientist launches alternative proposal for the currency|author=Alex Hern|date=17 August 2015|newspaper=the Guardian|access-date=20 August 2015}}{{Cite web |date=2022-04-29 |title=A list of Bitcoin forks and how they have changed the network - CNBC TV18 |url=https://www.cnbctv18.com/cryptocurrency/a-list-of-bitcoin-forks-and-how-they-have-changed-the-network-13318902.htm |access-date=2024-09-09 |website=CNBCTV18 |language=en}}

:On June 22, 2015, Gavin Andresen published BIP 101 calling for an increase in the maximum block size. The changes would activate a fork allowing eight MB blocks (doubling in size every two years) once 75% of a stretch of 1,000 mined blocks is achieved after the beginning of 2016.{{cite web|url=https://github.com/bitcoin/bips/blob/master/bip-0101.mediawiki|title=bips/bip-0101.mediawiki at master · bitcoin/bips · GitHub|work=GitHub}} The new maximum transaction rate under XT would have been 24 transactions per second.{{Cite news |url=http://www.pcworld.com/article/2974339/bitcoin-xt-debate-overshadowing-growth-opportunities.html |title=Bitcoin XT debate overshadowing growth opportunities |author=Tim Hornyak |access-date=7 January 2017 |date=21 August 2015 |work=PC World |publisher=IDG }}

:On August 6, 2015 Andresen's BIP101 proposal was merged into the XT codebase.{{cite web|url=https://github.com/bitcoinxt/bitcoinxt/commit/946e3ba8c7806a66c2b834d3817ff0c986c0811b|title=Implement hard fork to allow bigger blocks · bitcoinxt/bitcoinxt@946e3ba|website=GitHub}}{{cite web|url=https://github.com/bitcoinxt/bitcoinxt/releases/tag/v0.11A|title=bitcoinxt/bitcoinxt|website=GitHub}} Bip 101 was reverted{{cite web|url=https://github.com/bitcoinxt/bitcoinxt/pull/117|title=2MB block size bump by dgenr8 · Pull Request #117 · bitcoinxt/bitcoinxt|website=GitHub}} and the 2-MB block size bump of Bitcoin Classic was applied instead.{{cn|date=February 2021}}

:The August 2015 release of XT received widespread media coverage. The Guardian wrote that "bitcoin is facing civil war".

:Wired wrote that "Bitcoin XT exposes the extremely social—extremely democratic—underpinnings of the open source idea, an approach that makes open source so much more powerful than technology controlled by any one person or organization."{{cite magazine|url=https://www.wired.com/2015/08/bitcoin-schism-shows-genius-open-source/|title=The Bitcoin Schism Shows the Genius of Open Source|date=19 August 2015|magazine=WIRED|author=Cade Metz}} Developer Adam Back was critical of the 75% activation threshold being too low and that some of the changes were insecure.{{Cite news |url=https://www.cnbc.com/2015/08/20/bitcoin-splits-will-it-break-or-be-better-than-ever.html |title=Bitcoin splits: Will it break, or be better than ever? |author=Everett Rosenfeld |access-date=5 January 2017 |date=20 August 2015 |publisher=CNBC}}

:On August 25, 2017, Bitcoin XT published Release G, which was a Bitcoin Cash client by default.{{cite web|url=https://github.com/bitcoinxt/bitcoinxt/releases|title=Bitcoin XT Releases|website=GitHub |access-date=17 June 2018}} Subsequently, Release H was published, which supported the November 2017 Bitcoin Cash protocol upgrade, followed by Release I, which supported the May 2018 Bitcoin Cash protocol upgrade.{{cn|date=February 2021}}

; Bitcoin Classic: In its first 8 months, Bitcoin Classic promoted a single increase of the maximum block size from one megabyte to two megabytes.{{cite web|url=https://www.wsj.com/articles/is-bitcoin-breaking-up-1453044493|title=Is Bitcoin Breaking Up?|author=Paul Vigna|date=17 January 2016|work=Wall Street Journal}} In November 2016 this changed and the project moved to a solution that moved the limit out of the software rules into the hands of the miners and nodes.{{cite web |url=https://zander.github.io/posts/Classic%20is%20Back/ |title=Classic is Back |access-date=April 28, 2017 |archive-url=https://web.archive.org/web/20170202055402/https://zander.github.io/posts/Classic%20is%20Back/ |archive-date=2017-02-02 |url-status=dead}}

; Bitcoin Unlimited

All three software clients attempt to increase transaction capacity of the network. None achieved a majority of the hash power.{{cite book |title=The Bitcoin Standard: The Decentralized Alternative to Central Banking |last=Ammous |first=Saifedean |year=2018 |publisher=John Wiley & Sons |isbn=9781119473893 |pages=227, 228 |url=https://play.google.com/store/books/details?id=Pw5TDwAAQBAJ |access-date=23 April 2018}}

Hard forks splitting bitcoin (aka "split coins") are created via changes of the blockchain rules and sharing a transaction history with bitcoin up to a certain time and date. The first hard fork splitting bitcoin happened on 1 August 2017, resulting in the creation of Bitcoin Cash.

The following is a list of notable hard forks splitting bitcoin by date and/or block:

• Bitcoin Cash: Forked at block 478558, 1 August 2017, for each bitcoin (BTC), an owner got 1 Bitcoin Cash (BCH)
• Bitcoin Satoshi Vision: Forked at block 556766, 15 November 2018, for each Bitcoin Cash (BCH), an owner got 1 Bitcoin SV (BSV).
• eCash: Forked at block 661648, 15 November 2020, for each Bitcoin Cash (BCH), an owner got 1,000,000 eCash (XEC).
• Bitcoin Gold: Forked at block 491407, 24 October 2017, for each bitcoin (BTC), an owner got 1 Bitcoin Gold (BTG)

• The fork fixing the value overflow incident was controversial because it was announced after the exploit was mined. It was assigned [https://nvd.nist.gov/vuln/detail/CVE-2010-5139 CVE-2010-5139].

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Taproot is an agreed soft fork in the transaction format. The fork adds support for Schnorr signatures, and improves functionality of smart contracts and the Lightning Network. The fork was installed in November 2021.{{Cite news|last=Sigalos|first=MacKenzie|date=2021-06-09|title=Bitcoin just got its first makeover in four years|language=en-US|work=CNBC|url=https://www.cnbc.com/2021/06/12/bitcoin-taproot-upgrade-what-it-means.html|access-date=2021-06-15|issn=}} The upgrade adds privacy features.{{Cite news|last= Kharif|first=Olga|date=2021-06-15|title=Bitcoin to get more privacy features in Taproot update, making it harder to trace payments|language=en-US|work=Bloomberg|url=https://www.bloomberg.com/news/articles/2021-06-15/bitcoin-network-approves-privacy-update-as-scrutiny-increases|access-date=2021-06-23|issn=}}{{Cite news|last= Locke|first=Taylor|date=2021-06-14|title=7 key things that happened in crypto over the past week|language=en-US|work=CNBC|url=https://www.cnbc.com/2021/06/14/7-key-things-that-happened-in-crypto-over-the-past-week.html|access-date=2021-06-23|issn=}} Taproot includes Bitcoin Improvement Proposal numbers BIP340, BIP341, BIP342.{{Cite web |url=https://github.com/bitcoin/bips |title=All Bitcoin Improvement Proposals, including BIP340 |date=2021-06-01 |via=GitHub}}

Advantages:

• Complex transactions, such as those requiring multiple signatures or those with delayed release, are indistinguishable from simple transactions in terms of on-chain data.{{Citation needed|date=August 2021}}
• Reduced transaction costs: The data size of complex Bitcoin transactions is reduced, which leads to lower transaction fees.{{Citation needed|date=August 2021}}
• Support for more complicated conditions for a transaction via Schnorr signatures.{{Citation needed|date=August 2021}}
• Benefits for the Lightning Network: More flexibility, privacy enhancement, lower costs.{{Citation needed|date=August 2021}}

Three hard forks were created by "protocol change" definition:

• July 2010 Chain Fork (addition of OP_NOP functions)
• March 2013 Chain Fork (migration from BerkeleyDB to LevelDB caused a chain split)[https://github.com/bitcoin/bips/blob/master/bip-0050.mediawiki March 2013 Chain Fork]
• CVE-2018-17144 (Bitcoin 0.15 allowed double spending certain inputs in the same block. Not exploited)

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