What Is Optimism (OP)? Ethereum Rollups and the Superchain Explained

Optimism is one of Ethereum’s two dominant Layer 2 networks — alongside Arbitrum — and has become the foundation of a far larger ecosystem. By open-sourcing its technology as the “OP Stack,” Optimism enabled the creation of the Superchain: a growing network of interconnected rollups that includes Coinbase’s Base, the NFT platform Zora, and dozens of other chains.

How Optimism Works

Optimism is an optimistic rollup. Like Arbitrum, it bundles transactions, executes them off-chain, posts a summary to Ethereum, and relies on a 7-day fraud proof window for security. Any invalid transaction can be challenged and rejected during this window, inheriting Ethereum’s security guarantees.

The key difference from Arbitrum is in the fraud proof mechanism. Optimism originally used single-round fault proofs — simpler but more expensive to resolve. In 2023, Optimism upgraded to a permissionless fault proof system that allows anyone to challenge invalid transactions, moving it closer to true decentralisation.

The OP Stack: Building the Superchain

The most strategically significant decision Optimism made was open-sourcing its technology as the OP Stack. This allowed any team to deploy their own OP Stack chain — a rollup with the same underlying architecture, security model, and infrastructure as Optimism — in days rather than years.

The Superchain is the network of OP Stack chains sharing infrastructure, security, and (eventually) seamless communication. Key members:

Base (Coinbase): The largest OP Stack chain by usage, with millions of active users drawn in through Coinbase’s consumer products. Base has become the primary home for consumer crypto applications, social networks (Farcaster), and creator economy projects.

Zora: An NFT-focused chain where artists mint and sell digital work with very low fees. One of the most used chains for creative applications.