What is a Fork?
A fork is a change to a blockchain's rules or a split of the chain into two branches. Forks range from brief, routine chain splits to permanent divisions that create new coins, such as Bitcoin Cash.
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A fork is a change to a blockchain’s rules or a split of the chain into two separate branches. Not every fork creates a new coin. Some are natural splits that last seconds, some are planned software upgrades, and some divide a community and leave two permanent blockchains behind. When you see “fork” in a headline, it pays to work out which kind is meant.
What are the types of forks?
- Temporary chain split: when two miners find valid blocks at almost the same moment, nodes briefly follow different chain tips. Once the next block arrives, the chain with the most accumulated work wins and the other branch is abandoned. This is routine network behavior.
- Soft fork: a backward-compatible upgrade that tightens the rules. Older nodes that haven’t upgraded still accept the new blocks as valid.
- Hard fork: a change that isn’t compatible with the old rules, so nodes that don’t upgrade reject the new blocks. If everyone adopts it, the network carries on as one chain; if not, two chains emerge.
- Code fork: copying a project’s open-source code to launch a new blockchain. Litecoin was created from Bitcoin’s codebase this way in 2011. No existing chain history is split.
Notable forks in crypto history
Ethereum and Ethereum Classic (2016): an attacker exploited a flaw in a project called The DAO and drained a large amount of ETH. Most of the community backed a hard fork that reversed the losses; those who rejected it kept running the original chain, now known as Ethereum Classic (ETC).
Bitcoin Cash (August 1, 2017): after a long dispute over block size, a group favoring bigger blocks launched Bitcoin Cash (BCH) through a hard fork. Anyone holding BTC at the moment of the split also ended up with the same amount of BCH. Bitcoin Cash itself split again in November 2018, producing Bitcoin SV.
SegWit (2017) and Taproot (2021): both added new features to Bitcoin as soft forks, and the chain did not split.
Ethereum network upgrades: Ethereum ships planned upgrades such as London (2021), Dencun (2024) and Pectra (2025) as hard forks. Because the community adopts them broadly, no new coin appears.
The lesson from these episodes: software alone doesn’t decide which chain survives a fork. What matters is which chain miners or validators, exchanges, app developers and users choose to support.
What should you do when a fork happens?
For planned upgrades, people holding coins in their own wallets usually don’t need to do anything beyond keeping their wallet software up to date. Exchanges may pause deposits and withdrawals while the fork goes through.
If a chain split creates a new coin, claiming it typically involves your private keys. Never type your recovery phrase into a site promising to “claim your forked coins”; a safer approach is to move your original coins to a fresh wallet before claiming anything with the old keys. Also follow guidance from your wallet and exchange about replay attacks, where a transaction on one chain is rebroadcast on the other.
Frequently asked questions
Do forks give out free coins?
Only when the chain splits permanently do holders end up with matching coins on the new chain. Whether those coins get listed on exchanges, and what they’re worth, is uncertain.
What’s the main difference between a hard fork and a soft fork?
After a soft fork, old nodes still accept new blocks. After a hard fork, nodes that don’t upgrade reject the new chain.