Ethereum Classic is the original protocol of Ethereum. As a result of the massive hack on the Ethereum-based DAO, in which around 14% of all ETH in circulation were stolen, a hard fork was proposed to return the stolen funds to their owners. This caused an ideological split revolving around the question of changing previous transactions in the blockchain. Some Ethereum holders rejected the hard fork, and decided to keep using the original protocol, based on the principle that the blockchain is immutable, and cannot be changed.

Feathercoin is a PoW coin with a fast block processing time. The project was developed with the goal of creating a user friendly coin with fast transaction times and low fees. The Feathercoin network features Automatic Checkpointing (ACP), which is used to prevent 51% attacks. ACP creates a new checkpoint every 5 blocks, protecting the history of the Feathercoin blockchain.