OP Stack vs. Arbitrum Orbit: The Best L2 Rollup Comparison
Gelato Team
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May 15, 2025
Previous articles in this series:
TL;DR
Arbitrum and Optimism are leading Layer 2 scaling solutions for Ethereum, both optimistic rollups with 7-day challenge periods, but with different technical implementations.
OP Stack (Optimism) focuses on Ethereum alignment with strict EVM equivalence, a Superchain architecture for interchain communication, and a permissionless bisection protocol for fraud proofs using Cannon FPVM.
Arbitrum Orbit offers more flexibility with its Nitro stack, supporting both traditional Ethereum rollups and AnyTrust mode (using a Data Availability Committee), along with Stylus VM for non-EVM languages like Rust and C++, and a Universal Intents Engine that enables fast cross-chain operations through competitive solver execution.
Arbitrum emphasizes custom stack innovations that diverge from strict Ethereum equivalence—such as its AnyTrust DAC, fast withdrawal mechanisms, and Layer 3 strategy. In contrast, the OP Stack focuses on standardizing Ethereum-aligned practices, prioritizing equivalence and interoperability across its L2 Superchain ecosystem.
OP Stack is MIT open-source, with fees only applying when joining the Superchain (2.5% of revenue or 15% of onchain profit). Arbitrum uses a Business Source License with an "Additional Use Grant" allowing free L3s on Arbitrum One while requiring a 10% profit share for independent chains. Both systems have different approaches to revenue sharing, with OP focusing on collective governance while Arbitrum emphasizes "Your chain, your rules" flexibility.
OP-Succinct Lite and Arbitrum's BoLD protocol represent attempts to improve the traditional fraud proof mechanism, with the former using ZK proofs to reduce withdrawal times to 1 day.
Introduction
Arbitrum and Optimism provide optimistic Layer 2 scaling solutions for Ethereum that improve transaction speed and reduce costs while aiming to extend Ethereum's security...
What is an optimistic rollup?
State transitions are initially “optimistically” accepted without proofs but remain subject to a challenge period...
How L2 settlement happens
For optimistic L2s, Ethereum settlement specifically means having a smart contract light client bridge deployed on Ethereum that receives:
Data availability (DA) batches containing compressed transaction data
State root commitments that represent the updated L2 state
Fraud proofs that ensure the correctness of state transitions
OP Stack Architecture
Data availability and EVM compatibility
The OP Stack publishes compressed transaction batches to Ethereum to ensure data availability and security...
OP Fault Proof System
The Fault Proof System is a decentralized security mechanism...
Fault Proof Program (FPP): Verifies L2 state transitions...
Fault Proof Virtual Machine (FPVM): Executes the FPP...
Dispute Game Protocol: A permissionless system where users challenge invalid transactions...
Optimism Superchain
The Optimism Superchain is a unified network of interconnected L2 blockchains...
Source: docs.optimism.io/stack/interop/explainer
OP Stack special features
What are OP Flashblocks
Even 2-second block times on modern rollups like OP Stack L2s are too slow...
Removal of Custom Gas Tokens in Optimism
All new OP Stack chains must use ETH as the gas token...
What is OP altDA
Alt-DA mode allows for OP Stack chains to integrate with various DA Layers...
What are OP-Succinct ZK Fraud Proofs
Succinct and Optimism introduced OP Succinct Lite...
How OP Succinct Lite works in a nutshell
Transactions are processed offchain and assumed valid until challenged.
ZK proofs are generated only when disputes arise.
Disputes are resolved through onchain verification of these proofs.
The Arbitrum Orbit Stack
What is Arbitrum Orbit and How Orbit Rollup works
The Orbit stack utilizes the Nitro stack for its foundation...
Data availability and EVM compatibility
Arbitrum offers two operational modes for data availability: Rollup and AnyTrust...
Arbitrum’s Fraud Proof System
Arbitrum has a multi-round fraud proof system...
How Arbitrum AnyTrust works
AnyTrust allows chains to opt for a Data Availability Committee (DAC)...
Fast Withdrawals for AnyTrust Chains
Instead of the 7-day challenge period required by Optimistic Rollups...
Arbitrum L3s
An Arbitrum L3 chain is a chain that settles to an L2 chain...
L3 Chains Settle to Arbitrum, Not Ethereum
As mentioned earlier, Orbit’s L3 chains settle transactions on L2 chains...
Arbitrum Orbit expansion outside of Ethereum
Arbitrum is extending its reach beyond the Ethereum ecosystem...
Intent-based interop with Intents Engine
Unlike traditional transactions that define exact steps, intents express what you want accomplished...
How OP stack vs. Orbit differs
On Fraud Proof Systems
OP Stack uses optimistic rollups with a permissionless bisection protocol...
On Licensing and Fees
OP Stack is completely open-source with an MIT license...
Node Infrastructure
Arbitrum Nitro is the node software and architecture currently powering Arbitrum...
On VM Architecture
Optimism maintains strict EVM equivalence via op-geth...
Which to choose and why?
When evaluating Optimism's OP Stack and Arbitrum's Orbit, it becomes clear that each solution caters effectively to distinct segments of the Layer-2 market...
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Definitions
Optimistic Rollup: A scaling solution that processes transactions off-chain and posts transaction data to Ethereum...
Fraud Proof: A mechanism that allows participants to challenge and prove the invalidity of state transitions...
ZK Fraud Proofs: A hybrid approach that combines zero-knowledge proofs with fraud detection...
Validity Proofs (ZK Rollups): A model where every batch of transactions is accompanied by a cryptographic proof...
Data Availability (DA): Refers to how and where transaction data is published so that it can be independently verified...
Data Availability Committee (DAC): A permissioned group of trusted entities responsible for storing and serving transaction data off-chain...
Settlement: The process by which an L2 anchors its state to Ethereum...