What Is OP Mainnet? How It Works and How It Compares
“TL;DR: OP Mainnet is Optimism's Ethereum Layer 2 network. It processes transactions faster and at a fraction of Ethereum's cost, while using Ethereum for data availability and settlement. It is the original production network where the OP Stack was built and tested, and the starting point for teams before they launch their own dedicated chain.”
OP Mainnet is a public blockchain network built on the OP Stack that runs Ethereum-compatible transactions at significantly lower cost and higher throughput than Ethereum mainnet. Most applications that work on Ethereum can deploy on OP Mainnet with few or no smart contract changes. It posts transaction data back to Ethereum, which is where settlement and data availability come from.
OP Mainnet at a Glance
| Question | Answer |
|---|---|
| What is OP Mainnet? | A public Ethereum Layer 2 network built on the OP Stack |
| How does it work? | It executes transactions on L2, batches and compresses their data, and posts that data to Ethereum |
| What secures it? | Ethereum settlement and data availability, together with OP Mainnet's fault proof system |
| Is it EVM compatible? | Yes. Ethereum wallets, tools, and smart contracts generally work with few or no contract changes |
| How is it different from Ethereum mainnet? | It offers lower fees and more transaction capacity while settling back to Ethereum |
| How is it different from running your own chain? | OP Mainnet provides shared infrastructure and block space; a dedicated chain provides its own capacity, configuration, and economics |
How OP Mainnet Works
OP Mainnet is an optimistic rollup. It moves transaction execution away from Ethereum mainnet while continuing to use Ethereum for data availability and settlement.
The process has four parts:
- Users submit transactions to OP Mainnet. Ethereum-compatible wallets and applications send transactions to the network.
- OP Mainnet executes the transactions. Its sequencer orders transactions and produces L2 blocks.
- Transaction data is batched and posted to Ethereum. The data is compressed and submitted primarily through EIP-4844 blobs, reducing the cost of publishing it to Ethereum.
- State commitments can be challenged. OP Mainnet's fault proof system allows invalid state proposals to be challenged and verified against the data available on Ethereum.
What OP Mainnet Does
OP Mainnet was built to extend Ethereum's capacity without giving up Ethereum as the settlement layer. It batches transactions together, executes them away from the main chain, and posts compressed transaction data back to Ethereum at regular intervals.
The practical result: transaction fees that can run at fractions of a cent when network conditions allow, fast L2 block production, and compatibility with the Ethereum Virtual Machine, wallets, developer tools, and smart contracts. For users, it means applications that actually run at usable cost. For developers, it means the same Solidity contracts they'd write for Ethereum, usually deployed with few or no contract changes. For enterprises, it means Ethereum settlement and an onchain audit trail at the throughput and cost structure that makes production infrastructure viable.
Why It Was Built
Ethereum was the most credibly neutral settlement layer ever built. The problem was scaling it without sacrificing what made it worth trusting.
Optimism deployed OP Mainnet in January 2021 as one of the first major optimistic rollups in production, opening it to permissionless deployment by the end of that year. It was not a testnet or a research prototype. It was a live network carrying real transaction volume, built to prove that the OP Stack architecture could work under production conditions.
Every subsequent development on the OP Stack, including the fault proof system and interoperability work, has been tested against the demands of running production L2 infrastructure. The open-source implementation is available in the OP Stack repository.
The OP Mainnet Ecosystem
OP Mainnet is a shared public network. Open to any developer, user, and permissionless application.
It carried roughly $340M in DeFi TVL as of June 2026, as measured by DefiLlama, with about $1.4B in total value secured per L2Beat. Because these figures change continuously, current numbers should be checked through DefiLlama's Optimism dashboard.
DeFi Applications on OP Mainnet
OP Mainnet supports Ethereum-compatible decentralized exchanges, lending markets, liquid staking products, stablecoin infrastructure, and other financial applications.
ether.fi migrated $220M in TVL from Scroll in three days: 300,000 accounts, 70,000 Visa debit cards, $2 million in daily payment volume, zero downtime. The full migration is documented in the ether.fi OP Mainnet case study.
Payment Solutions on OP Mainnet
Low transaction costs and Ethereum-compatible infrastructure make OP Mainnet usable for payment applications that need to process frequent onchain activity.
The ether.fi migration included 70,000 Visa debit cards and $2 million in daily payment volume. The application moved without replacing the underlying EVM development model.
Identity and Consumer Applications on OP Mainnet
World, the identity network with tens of millions of users, started here before graduating to its own OP Stack chain.
That path moved from an application on shared OP Mainnet infrastructure to a dedicated chain built for its own scale and economics. The transition is documented in the World Chain case study.
Institutional Assets on OP Mainnet
Mitsui & Co. Digital Commodities brought Zipangcoin to OP Mainnet, issuing the Japanese institution's commodity-backed digital asset on a public blockchain for the first time.
OP Mainnet vs. Ethereum Mainnet
OP Mainnet and Ethereum mainnet are not alternatives to each other. OP Mainnet is a scaling layer that runs on top of Ethereum. Assets and data move between the two. OP Mainnet uses Ethereum for settlement and data availability, while also operating its own execution environment, sequencer, fault proof system, and upgrade process.
| OP Mainnet | Ethereum Mainnet | |
|---|---|---|
| Transaction cost | Commonly fractions of a cent, but variable | Variable and often higher |
| Block time | About 2 seconds | About 12 seconds |
| Security model | Ethereum settlement and data availability, with fault proofs and additional L2 operational assumptions | Native Ethereum proof-of-stake consensus |
| Smart contract support | EVM equivalent, with some L2-specific differences | Native EVM |
| Transaction execution | Executed on OP Mainnet | Executed directly on Ethereum |
| Withdrawals to Ethereum | Standard withdrawals require a challenge period | No L2 challenge period |
| Best for | Applications, DeFi, payments, and user-facing activity | High-value settlement and activity that must execute directly on L1 |
The same wallets, developer tools, and Solidity contracts generally work on OP Mainnet. Applications still need to account for network configuration, contract addresses, bridges, data sources, and other L2-specific behavior.
For most applications, OP Mainnet is where transactions happen and Ethereum is where data and settlement are anchored. Independent network risk and maturity assessments are available through L2Beat.
OP Mainnet vs. Running Your Own Chain
OP Mainnet is a public network with shared block space. That means no dedicated throughput, no custom transaction fee structure, and no direct control over sequencer economics. For most teams starting out, that is exactly right: no chain infrastructure to manage, no sequencer to operate, and immediate access to an existing user base and application ecosystem.
A dedicated OP Stack chain gives a team its own block space, configuration, governance decisions, and economics. It also creates infrastructure, security, interoperability, and operational responsibilities that the team does not carry when deploying an application on OP Mainnet.
| OP Mainnet | Dedicated OP Stack Chain | |
|---|---|---|
| Block space | Shared | Dedicated |
| Infrastructure | Operated as part of OP Mainnet | Operated or managed for the chain |
| Fee configuration | Set at the network level | Configurable by the chain |
| Sequencer economics | Shared network economics | Chain-specific economics |
| Initial ecosystem | Existing OP Mainnet users and applications | Must be developed or connected |
| Best for | Teams launching and proving an application | Teams that need dedicated scale, configuration, or economics |
The teams that move beyond OP Mainnet do so when dedicated infrastructure makes economic sense. The transition does not require a new smart contract platform. The same OP Stack architecture, tooling, and developer experience move with the team.
OP Mainnet is where the proof of concept becomes a production application. A dedicated chain is where a production application becomes a business with its own economics.
Should You Use OP Mainnet, Ethereum Mainnet, or Your Own Chain?
Use OP Mainnet when an application needs low-cost, Ethereum-compatible transactions without operating chain infrastructure.
Use Ethereum mainnet when activity must execute directly under Ethereum's native consensus and the additional cost and limited capacity make sense for the application.
Run your own OP Stack chain when dedicated block space, custom configuration, or chain-specific economics justify the infrastructure and operational responsibility.
For most teams, OP Mainnet is the place to start.
Frequently Asked Questions
Is OP Mainnet the same as Optimism?
OP Mainnet was previously called "Optimism." It was renamed in June 2023 to distinguish the network from the broader Optimism ecosystem and the OP Stack technology framework.
OP Mainnet refers specifically to the public Layer 2 network. OP Stack refers to the open-source technology. Optimism refers to the broader ecosystem, while OP Labs is a core development company contributing to both.
Is OP Mainnet secure?
OP Mainnet uses Ethereum for settlement and data availability. Transaction data is posted to Ethereum, and OP Mainnet's fault proof system allows invalid state proposals to be challenged.
The security model also includes L2-specific components, including the sequencer, bridge contracts, the upgrade process, the fault proof implementation, and a Security Council that can intervene in emergencies. Users can review the current system configuration and risks through the OP Mainnet documentation and L2Beat, which rates OP Mainnet as a Stage 1 rollup.
How does OP Mainnet keep fees low?
OP Mainnet batches transactions and compresses their data before posting it to Ethereum. With EIP-4844 blobs, introduced in Ethereum's Dencun upgrade in March 2024, the cost of posting rollup data dropped significantly.
OP Mainnet fees reflect L2 execution costs and the cost of publishing data to Ethereum rather than the full cost of executing every transaction directly on Ethereum mainnet. Fees remain variable and depend on activity on both networks.
How fast is finality on OP Mainnet?
OP Mainnet produces blocks in about 2 seconds, but a block appearing on OP Mainnet is not the same as Ethereum finality.
A transaction first receives an L2 confirmation. It later becomes safer once its data has been posted to Ethereum, and it follows Ethereum's own confirmation and finality process after that. Standard withdrawals from OP Mainnet to Ethereum require a challenge period of about seven days before they can be executed on L1.
What can you build on OP Mainnet?
Anything supported by its Ethereum-compatible execution environment can run on OP Mainnet. That includes DeFi protocols, payment applications, NFT platforms, stablecoin infrastructure, identity applications, and enterprise financial applications.
The network has been live since 2021 and carries hundreds of deployed applications.
What is the OP Stack?
The OP Stack is the open-source software framework that powers OP Mainnet and chains launched using the same architecture. Its core codebase is MIT-licensed, meaning any team can use it, fork it, and build on it.
OP Mainnet is both the original production deployment of the OP Stack and the shared public network anyone can use today. Teams evaluating a dedicated chain can start with the OP Stack documentation.
OP Mainnet Resources
Authored by
Optimism