• Two-three miners mining at the same time to create new a block.
• Bitcoin cash was created by fork in the bitcoin .

In consideration to cryptocurrency, fork means split in blockchain in two separate branches. The network shares the common history until they get split, after that they both record the transaction independently in their own direction. 

There are many reasons when a fork can occur, it can be intentional or accidental. Intentional fork further can be classified into two parts: soft fork and hard fork

Features of blockchain fork –

• A blockchain splits into two competing branches
• Blockchain can be fork in two ways: accidentally and intentionally
• Accidental fork is resolved by the blockchain 
• To implement new consensus rule intentional fork is used 
• Hard fork require nodes to be upgraded to the new consensus rule 
• Soft fork doesn’t require to upgrade to new consensus rule 
• Bitcoin cash was created using hard fork. 

Accidental fork

At a time, there are thousands of miners mining the network, to create a new block. With so much mining going at the same time, two-three miners, trying to create new block at the same time, which in result, split the blockchain into two parts, and this type of split in blockchain is known as accidental fork. This gets resolved when a new block is added to one of the chain. When this fork happens, chain continues to work on the longer chain and abandons the shorter chain.

Intentional Fork 

An intentional fork is made by the developer intentionally to make changes on the protocol. Intentional fork do not reconverge on a single chain. Developers use intentional fork for a variety of reasons such as to increase block size, reduce blocktime or to implement an entirely new blockchain consensus algorithm. Further intentional fork can be classified in two categories : hard and soft fork, both differ from each other in terms of compatibility with the other chain and their application.  

Hard fork –

In hard fork, community implement new rules in the network and require nodes in the network to upgrade the software. For example – blockchain stores only 1 MB data in a block and it wants to increase the size from 1MB to 5 MB, then nodes have to set the new rules for the software which will exceed the storage size of the block in blockchain. This will result in a hard fork.

In hard fork, community members have to make decision. Whether they want to update to a new node or they want to continue with the old network. In both the cases, user doesn’t lose anything, the only advantage is that, user can claim for new chain of the new protocol.

Soft fork –

On the other hand, in soft fork, the new block created under new rules are also valid under the old rules therefore nodes don’t need to upgrade to participate in the network, they can take part with the old software and act as a validator of the transactions. Soft fork can be activated by the users and miners. This makes the chain forward compatible.

Example of fork

Some of the popular blockchain are created by fork like bitcoin cash which was forked from bitcoin in August 2017, bitcoin cash changed the block size from 1MB to 8MB and then further to 32 MB.