Ethereum ETH: Istanbul Testnet Hard Fork

What is a hardfork?

The cryptocurrency mainnet operates according to certain rules. To improve network performance or correct errors, changes are periodically introduced into it. A hard fork represents changes that are not compatible with previous versions of software supporting the cryptocurrency network. In order to continue to mine the cryptocurrency, miners need to update the software.

In some cases, as a result of a hard fork, a completely new cryptocurrency may appear, as happened with Bitcoin Cash and EthereumPoW.