Arbitrum and Optimism are the two largest Ethereum Layer 2 networks by total value locked. Both aim to make Ethereum transactions faster and cheaper by processing activity off the main chain and settling results on Ethereum. They share a similar category — optimistic rollups — but differ in their technical architecture, ecosystem maturity, and governance model.
What they have in common
Both Arbitrum and Optimism are optimistic rollup networks. "Optimistic" means they assume transactions are valid by default and only run fraud proofs if a challenge is submitted. This approach allows for high EVM compatibility — most Ethereum smart contracts deploy on both networks with minimal modification. Both use ETH as the gas token for most applications, and both ultimately settle transaction data on Ethereum mainnet, inheriting Ethereum's security guarantees.
How Arbitrum differs
Arbitrum (built by Offchain Labs) uses its own virtual machine — the Arbitrum Virtual Machine (AVM), now the Stylus VM — which is a superset of the Ethereum Virtual Machine. This allows Arbitrum to support contracts written in Rust and C++ in addition to Solidity, expanding developer options. Arbitrum's fraud proof system (multi-round interactive fraud proofs) is designed to minimize the amount of computation that needs to happen on-chain in a dispute, making challenge resolution cheaper.
Arbitrum One is the primary network. Arbitrum Nova is a separate, higher-throughput chain designed for gaming and social applications using a different data availability model (AnyTrust).
How Optimism differs
Optimism (built by OP Labs) introduced the "Superchain" concept: a framework where multiple chains share a standard tech stack (the OP Stack) and can interoperate. Base (Coinbase's L2), Zora, and Mode Network are all built on the OP Stack, meaning activity on those chains contributes to Optimism's broader ecosystem and governance token (OP).
Optimism uses single-round fraud proofs and has been more aggressive about open-sourcing its rollup infrastructure for other teams to build on.
Key differences at a glance
| Arbitrum | Optimism | |
|---|---|---|
| VM compatibility | EVM + Rust/C++ via Stylus | EVM compatible |
| Ecosystem model | Standalone + Orbit L3s | Superchain (OP Stack) |
| Governance token | ARB | OP |
| Notable L2s using the stack | Arbitrum Nova | Base, Zora, Mode |
| Fraud proof type | Multi-round interactive | Single-round |
Which is right for you?
For most users interacting with DeFi applications, both networks are functionally equivalent: similar fees, similar speeds, and the same major protocols (Uniswap, Aave, Curve) are deployed on both. Arbitrum currently leads in total value locked and DeFi depth. Optimism's Superchain ecosystem gives it broader reach across consumer apps and NFT platforms.
For developers, the choice depends on tooling preference and whether you want access to Stylus (Arbitrum) or want to build a chain on the OP Stack (Optimism ecosystem).
Neither ARB nor OP token performance should factor into a technical choice between the networks.