OP Mainnet is the first network in the OP Ecosystem and was developed by the Optimism Foundation. It is a low-cost and very fast Layer 2 (L2 Ethereum) blockchain created for the efficient scaling of Ethereum-based applications. The tool is intended for Ethereum developers and features the same software with similar performance as EVM-based development tools. If an app is on Ethereum, it would also be supported on the OP Mainnet, but at a lower cost.

The Optimism Foundation is a nonprofit organization that seeks to preserve and protect the benefits of Ethereum by designing and implementing systems for the emergence and development of public goods. The foundation has achieved several milestones such as the development of Optimistic Rollup, several testnets, and movement towards a complete decentralized sequencer. The foundation's philosophy is to scale Ethereum technology and values by supporting high-impact projects that lack a traditional business model.