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Crypto Glossary/Hard Fork (Blockchain)

Hard Fork (Blockchain)

A hard fork is a non-compatible upgrade to a blockchain that creates two separate chains. It is used to introduce new features, improve security, or resolve conflicts. Examples include Bitcoin

TLDR - Hard Fork (Blockchain)

A hard fork is a type of upgrade or modification made to a blockchain protocol that is not backward-compatible. It involves a permanent divergence from the existing blockchain, resulting in two separate chains with different rules and features. Hard forks are typically implemented to introduce significant changes, such as adding new functionalities, improving security, or resolving conflicts within the network.

What is a Hard Fork?

A hard fork is a fundamental change to the protocol of a blockchain network that renders previous versions of the software incompatible with the new version. It involves a permanent split in the blockchain, resulting in two separate chains that continue to exist independently. This means that nodes running the old version of the software will not be able to validate transactions or interact with nodes running the new version, and vice versa.

How Does a Hard Fork Work?

When a hard fork occurs, the blockchain network undergoes a significant upgrade or modification that introduces new rules and features. These changes are not backward-compatible, meaning that nodes running the old version of the software will not recognize or accept blocks created by nodes running the new version.

During a hard fork, the blockchain splits into two separate chains. One chain follows the old set of rules and continues to operate as it did before the fork, while the other chain adopts the new set of rules and incorporates the changes introduced by the fork. Both chains share the transaction history up until the fork but develop independently from that point forward.

Reasons for Implementing a Hard Fork

Hard forks are typically implemented for various reasons, including:

  • Adding new functionalities: A hard fork can be used to introduce new features or functionalities to a blockchain network. This could include improvements to scalability, privacy, or smart contract capabilities.
  • Improving security: If a vulnerability or flaw is discovered in the blockchain protocol, a hard fork can be implemented to fix the issue and enhance the security of the network.
  • Resolving conflicts: In some cases, there may be disagreements within the community or development team regarding the direction of the blockchain. A hard fork can be used to resolve these conflicts by creating a separate chain that follows a different set of rules.

Examples of Hard Forks

There have been several notable hard forks in the history of blockchain technology. Here are a few examples:

  • Bitcoin Cash (BCH): Bitcoin Cash is a hard fork of Bitcoin that occurred in August 2017. It was implemented to increase the block size limit of the Bitcoin blockchain, allowing for faster and cheaper transactions.
  • Ethereum Classic (ETC): Ethereum Classic is a hard fork of Ethereum that took place in July 2016. It was the result of a disagreement within the Ethereum community regarding the handling of a security breach. Ethereum Classic continued to operate on the original blockchain, while Ethereum moved forward with the changes.
  • Bitcoin SV (BSV): Bitcoin SV is a hard fork of Bitcoin Cash that happened in November 2018. It aimed to restore the original vision of Bitcoin by increasing the block size and enabling more transactions per second.

Challenges and Considerations

While hard forks can bring about significant improvements and changes to a blockchain network, they also present challenges and considerations:

  • Network consensus: Achieving consensus among network participants is crucial for a successful hard fork. If there is not enough support or agreement within the community, the fork may result in a split with limited adoption.
  • Community fragmentation: Hard forks can lead to a fragmentation of the community, as different factions may choose to support different chains. This can result in a loss of network effects and a decrease in overall network security.
  • Upgrade coordination: Coordinating the upgrade process and ensuring that all participants are aware of and prepared for the fork can be challenging. Failure to properly communicate and coordinate the fork can lead to confusion and potential loss of funds.


A hard fork is a significant upgrade or modification to a blockchain network that results in a permanent divergence from the existing chain. It introduces new rules and features that are not backward-compatible, leading to the creation of two separate chains. Hard forks are implemented to add new functionalities, improve security, or resolve conflicts within the network. While they can bring about positive changes, hard forks also present challenges such as achieving consensus, community fragmentation, and upgrade coordination.

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