A sidechain (or side chain) is an external secondary blockchain protocol that is connected to a primary blockchain network (mainchain). Sidechains are typically designed to allow for the transfer of data and value between themselves and the mainchain, and oftentimes use a different consensus mechanism than the mainchain. As a result, sidechains can allow for a higher degree of flexibility and scalability, given that systems with a significant sidechain interoperability component are often designed to cater to a broader range of enterprise and individual users. For example, some sidechain solutions allow for the transfer of assets back and forth between multiple protocols like Ethereum and Bitcoin. Other examples of sidechain capabilities include enhancements used for Layer-2 scaling solutions to increase the transaction speeds of the mainchain.
