The OP Stack is an open-source software framework for building layer 2 blockchains on top of Ethereum. It was developed for Optimism and powers OP Mainnet, Base and a growing number of other chains. Instead of building a rollup from scratch, teams use the OP Stack's standard components and configure them for their own chain.
How the OP Stack Works
Chains built on the OP Stack are optimistic rollups. A sequencer orders user transactions and produces blocks quickly and cheaply. The transaction data is published to Ethereum, so anyone can reconstruct the chain's state. Results are assumed to be correct unless someone proves otherwise during a challenge period, using fault proofs. That challenge period is why withdrawing directly from an optimistic rollup to Ethereum takes several days, unless a bridge or liquidity provider is used.
The Superchain
Chains that share the OP Stack and its governance form what Optimism calls the Superchain: a network of layer 2s with shared standards and upgrades, aiming for easier interoperability between them. For developers, this means that an application built for one OP Stack chain usually works on the others with little or no change.
What It Means for Applications
- EVM equivalence: Solidity contracts and Ethereum tools work as on Ethereum.
- Low fees: transactions cost a fraction of mainnet, with an extra component for publishing data to Ethereum that fee estimation must include, see EIP-1559 fee handling.
- Withdrawal times: plan for the challenge period when moving funds back to Ethereum.
- Sequencer dependency: transaction ordering depends on the sequencer, which matters for uptime and for MEV.
See Optimism development, Base development and layer 2 development.
Frequently Asked Questions
Is Base built on the OP Stack?
Yes. Base, launched by Coinbase, is one of the best-known chains built on the OP Stack.
What is the difference between the OP Stack and Arbitrum?
Both are optimistic rollup technologies. Arbitrum uses its own stack (Nitro and Orbit for custom chains); the OP Stack is Optimism's framework. They differ in fraud-proof design, tooling and governance.
Can anyone launch a chain with the OP Stack?
The code is open source, so technically yes. Joining the Superchain and its shared standards involves governance and agreements with Optimism.