Fork

Blockchains are not frozen in time. Their software gets upgraded, bugs get fixed, and sometimes communities disagree so strongly that they go separate ways. When a blockchain's rules change, people call it a fork. Some forks happen quietly in the background, while others create entirely new cryptocurrencies overnight.

What Does Fork Mean?

In crypto, a fork happens when a blockchain's rules are changed, causing the chain to follow a new path from a specific block onward. Every node on a network runs software that enforces the same rules. When those rules change, nodes must choose whether to upgrade. If everyone upgrades, the network continues as one. If some refuse, the chain can split in two.

Imagine a road that suddenly divides at a junction. Everyone traveled the same road up to that point, so they share the same journey so far. After the junction, some drivers take the left path and others take the right, and from then on they head to different places. A blockchain fork works the same way: both chains share the same history up to the split, then continue separately.

How Forks Work

Blockchain software is usually open source, so anyone can propose changes. Developers write the new code, the community debates it, and node operators, miners, or validators decide whether to run it.

The Fork Point

Every fork has an activation point, usually a specific block number or time. Before that point, all nodes follow the old rules. After it, upgraded nodes follow the new rules. Whether the network stays united depends on how compatible the new rules are with the old ones.

Why Forks Happen

Forks are often used to add new features, improve security, increase capacity, or fix bugs. Sometimes they are used to undo the effects of a major hack. Occasionally, they happen because a community cannot agree on the project's direction.

Types of Forks

There are two main kinds of blockchain forks, plus a third use of the word that you will see in crypto conversations.

Soft Forks

A soft fork is a backward-compatible upgrade. It tightens or adds rules in a way that older nodes still accept as valid. Nodes that do not upgrade can keep following the chain, although they may not understand every new feature. Bitcoin's SegWit upgrade, activated in 2017, is a well-known example of a soft fork.

Hard Forks

A hard fork is not backward compatible. Blocks created under the new rules are rejected by nodes running the old software. If everyone upgrades, the network simply moves forward. If a meaningful group refuses, the result is two separate blockchains, each with its own coin.

Code Forks

Developers also use "fork" to mean copying an existing project's open-source code to start a new one. Many altcoins and DeFi apps began as forks of Bitcoin, Ethereum, or popular protocols, with a few changes to the original design.

Famous Forks in Crypto History

Several forks have shaped the crypto landscape and show how forks play out in practice.

• Ethereum and Ethereum Classic: In 2016, after a hack drained funds from a project called The DAO, the Ethereum community hard forked to return the funds. A group that rejected the change kept the original chain running as Ethereum Classic.
• Bitcoin Cash: In August 2017, a disagreement about block size led to a hard fork that created Bitcoin Cash, which allowed larger blocks than Bitcoin.
• Planned network upgrades: Many hard forks are not splits at all. Ethereum regularly ships coordinated upgrades, including the Merge in September 2022, which moved the network to proof-of-stake.

What Happens to Your Coins During a Fork

If a fork is a smooth upgrade that everyone adopts, nothing changes for you. Your coins stay where they are, and you usually do not need to take any action unless you run your own node.

If a hard fork splits the chain, anyone who held coins at the fork point typically ends up with a balance on both chains. For example, people who held Bitcoin when Bitcoin Cash split off received an equal amount of the new coin. Whether you can access the new coins depends on your wallet or exchange, since each platform decides which forked chains to support.

Risks and What to Watch For

Forks can create opportunities, but they also bring confusion and risk.

• Scams: Fraudsters often promote fake wallets or "claim tools" around forks to steal private keys. Only use trusted software, and never enter your seed phrase on an unfamiliar site.
• Replay attacks: If a split chain lacks proper protection, a transaction on one chain could be copied onto the other. Many teams add replay protection, but it is worth checking before you move funds.
• Exchange pauses: Exchanges may temporarily stop deposits and withdrawals around a fork, so plan transfers ahead of time.
• Value uncertainty: A newly forked coin may have little liquidity or support, and its price can swing wildly.

When a major fork is coming, follow official announcements from the project and your wallet or exchange. Avoid rushing, and be wary of anyone promising free coins in exchange for your keys.

Useful Links

• What is a fork in crypto?
• What is the complete history of Bitcoin?
• What is blockchain?
• What is a consensus mechanism?