Notable Forks That Have Happened in the Past – OpenChat Foundation – Medium
What is a Hard Fork?
A hard fork is a permanent change in the blockchain from previous versions of the blockchain and nodes running previous versions will no longer be accepted by the newest version. The hard fork results in two different chains, one with the older version of the blockchain and one with the new chain. All the users and nodes need to upgrade to the newer version of protocol.
Here are summaries for a couple of the most successful hard forks to have ever taken place:
1. Bitcoin Cash: Bitcoin Cash split from bitcoin on August 1st, 2017. At that time, there were huge uncertainties surrounding the split and how the split would occur. Huge sell-offs took place a week before the fork happened, dropping the price of bitcoin by more than half. The bitcoin community debated for about a year on the bitcoin block size of 1mb, a block size that was causing high transaction fees and slow transfers on the networks.
2. Ethereum Fork From Ethereum Classic: It is not a commonly known fact that Ethereum was hard forked from Ethereum Classic as part of a $56 million dollar bailout. The hard fork resulted in a chain split. The DAO team had three options, either choose to do nothing, soft fork, or implement a hard fork. The team had 28 days to work on either of the three options. In the end the DAO chose to hard fork.
3. Zclassic Hard Fork: Zclassic was a hard fork of Zcash. Zcash was forked with the intention of avoiding the “Founder’s Reward”, which basically meant that for every transaction that takes place in the Zcash chain a part of the transaction fee is paid to the founders. To avoid this the Zclassic hard fork was executed.
What is a Soft Fork?
A soft fork is like a software update to the current code version for the protocol. A soft fork is a change to the protocol wherein only previously valid blocks/transactions are made invalid. Since old nodes will recognize the new blocks as valid, a soft fork is backward-compatible. When the majority of miners upgrade to accept new rules, it is called a miner-activated soft fork (MASF). When full nodes coordinate to accept new rules, without support from miners, it is called a user-activated softfork (UASF).
Here are summaries for a couple of the most well-known soft forks to have ever taken place:
1. BIP66 Blockchain Fork: After the deployment of the BIP66 soft fork in 2015, 95% of hash power stated that they accepted BIP66 by setting their block version to 3. In theory, setting your block version to 3 is an agreement with the network to consider version 2 blocks invalid and only mine on valid forks. Being part of the 5% that hadn’t updated and weren’t creating version 3 blocks, BTCNuggets created a version 2 block which was invalid to all new clients (>=0.9.5) but valid to old clients. Antminer and F2Pool, comprising ~40% of the network at the time, were creating version 3 blocks, however neither miner validated previous blocks. This caused both Antminer and F2Pool to mine on top of BTCNuggets version 2 block and create an invalid fork. Over 40% of the hashpower was mining on this version 2 fork despite 95% having “agreed” to not do so. This led to a 6 block fork that was resolved after contacting the F2Pool and Antminer pool owners.
2. Bitcoin SegWit Update: When SegWit was activated, a new class of addresses (Bech32) was created. But those using older P2SH addresses were not affected by the addition. A full node running version 0.1 of the Bitcoin Core software could send a non-SegWit transaction to a node running updated SegWit software and the transaction would still go through.