Overview of Bitcoin Forks

This is the first of the two-part article on forks. Here we give a short overview of bitcoin forks in chronological order
A fork is a divergence in a blockchain which splits it in two chains. Major changes in protocols are introduced by way of hard forks, while minor improvements are implemented in soft forks.
Bitcoin XT
Bitcoin XT is one of the earliest bitcoin forks initiated by Mike Hearn in December 2014. Originally, Bitcoin XT implemented new features suggested by Hearn in BIP64. Bitcoin XT gained notoriety in 2015 with the proposal of gradually raising the block size limit from 1MB to 8MB, outlined in Gavin Andresen’s BIP101. This change was not received warmly by the community. Today, Bitcoin XT is practically dead.
Bitcoin Classic
Bitcoin Classic was another attempt to address bitcoin scalability issues by raising block size limit. Bitcoin Classic was launched in 2016 proposing a 2MB blocks. While the project did gain some traction, it never really achieved a critical user base and got abandoned.
Bitcoin Unlimited
Bitcoin Unlimited is a bitcoin hard fork which lets miners customize the block size limit, which is 16MB by default. Initially, Bitcoin Unlimited showed ambitions capturing a relatively wide audience. However, the fork lost most of its popularity due to certain bugs that disrupted the network operation.
Segregated Witness
Segregated Witness (SegWit) is a bitcoin soft fork which increases block capacity by reducing the size of the transaction. SegWit was proposed by Bitcoin Core developer Peter Wuille in 2015. SegWit stores transaction signatures in another structure called an extended block, which frees up space for transactions in the mainchain block. Other advantages to SegWit include a fix to transaction malleability, which in turn enables second-layer solutions such as Lightning Network and atomic swaps.
Bitcoin Cash
Bitcoin Cash is a bitcoin hard fork activated in August 2017. The block size limit is Bitcoin Cash is 8MB. Bitcoin Cash quickly gathered support from major influencers, such as Roger Ver and ViaBTC. Bitcoin Cash does not support SegWit. Though Bitcoin Cash is now losing popularitydue to exceeding controversy surrounding it, it is still one of the most widely adopted forks.
Bitcoin Gold
Bitcoin Gold is a bitcoin hard fork activated in October 2017. Bitcoin Gold aims to restore the mining functionality with common graphics cards, in place of mining with specialized ASICs, used to mine Bitcoin. Due to multiple attacks successfully executed on the network, Bitcoin Gold is not seeing popularity among crypto-enthusiasts.
SegWit2x
SegWit2x was outlined in the New York Agreement signed by prominent figures in the space. SegWit2x proposed the activation of SegWit and a 2MB block size limit. The community naturally did not approve of the shady reunion, and the project failed.
Ethereum Constantinople
Ethereum Constantinople is an upcoming hard-fork of Ethereum. Constantinople is the second stage of the Metropolis upgrade. It seeks to reduce transaction fees and improve the overall efficiency of the Ethereum network. Constantinople will introduce four EIPs (Ethereum Improvement Proposals) which will reorganize the way how block hashes are stored and increase the speed of arithmetic in EVM (Ethereum Virtual Machine). The Ethereum Constantinople devs meeting is to take place on August 31 at 14:00 UTC.
Ethereum Classic (ETC)
Ethereum Classic (ETC) forked from Ethereum in July 2016. Ethereum Classic was born as the result of a major attack on the DAO, a failed blockchain rendition of a venture capital fund. Due to a combination of vulnerabilities, the attacker was able to siphon $50 million worth of ethers. To repair the damage, Ethereum forked reverting fraudulent transactions. A relatively large part of the community however did not agree with the decision and stuck with the old chain, hence Ethereum Classic. It is one of the more popular forks with an hourly average of 2,000 transactions.
EtherZero (ETZ)
EtherZero (ETZ) is another fork of Ethereum activated in January 2018. EtherZero is promoted as a zero-fee instant-pay smart-contract platform utilizing a masternode system. Despite that, the fork is far from seeing any recognition from the community with the 24-hour trading volume of measly $156.
EthereumFog (ETF)
EthereumFog (ETF) is yet another minor Ethereum fork which split from the main chain in December 2017. Based in China, EthereumFog markets itself as a fog-computing platform which fixes the problem of scalability and is dedicated to building business partnerships. EthereumFog market is largely unpopulated with $372 worth of transactions in past 24 hours.
Ethereum Modification (EMO)
Ethereum Modification (EMO) hard-forked from Ethereum main chain in December 2017. EMO’s features include the template contact, a separate accounts model, and natural fork, as the core concept of the fork. EMO’s official github page and social media accounts do not seem to have much content.
