Fork (hard fork and soft fork)
A fork is a change to a blockchain's rules or a split of its chain. A soft fork stays compatible with old nodes; a hard fork does not, and if part of the network refuses it, a second coin appears.
How it works
A blockchain's rules live in the software that nodes run. To change something, add a feature or fix a bug, developers release a new version. If the new rules are only stricter than the old ones, old nodes still accept the blocks. That is a soft fork. An example is SegWit on bitcoin (2017).
If the new rules allow something that used to be forbidden, old nodes start rejecting new blocks. That is a hard fork, and everyone has to upgrade. When the community agrees, it is just a planned upgrade. When it does not, the chain splits in two, each with its own coin. That is how Bitcoin Cash appeared in 2017, and how Ethereum split into Ethereum and Ethereum Classic in 2016.
"Fork" also means copying code: developers take a project's open-source code and launch their own network or app on it. Many DEXs and altcoins are forks of someone else's code. Such forks do not give coins to holders of the original.
You held 1 BTC in your own wallet when the network split in August 2017. After the hard fork you still had 1 BTC plus 1 BCH, because history before the split is shared. Only people who controlled their keys, or held coins on an exchange that supported the fork, could claim the BCH.
A common mistake is believing every fork is "free money". The new coin is often worth little and falls fast, and scammers ride the hype by asking you to enter your seed phrase to "claim fork coins". Never type your seed phrase into a website; for a real fork, follow your wallet's official instructions.
Questions and answers
What is a fork in simple terms?
It is a change to a blockchain's rules. If some participants reject the new rules, the network splits into two chains.
What is the difference between a hard fork and a soft fork?
A soft fork works with older software versions, a hard fork does not. After a hard fork, nodes that did not upgrade end up on a separate chain.
Do I get new coins in a fork?
If the chain splits and you held coins at that moment, you have coins on both chains. On an exchange it depends on whether the exchange supports the fork.
Related terms
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Updated: 2026-10-19