Not so fast! This article compares Arbitrum and Optimism to analyze if one L2 really can decisively win the scaling battle. We will analyze:The blockchains’ architecture.An ecosystem comparison.Future catalysts.Join us in showcasing the cryptocurrency revolution, one newsletter at a time. Subscribe now to get daily news and market updates right to your inbox, along with our millions of other subscribers (thats right, millions love us!) what are you waiting for?Ethereum is scaling natively with a detailed roadmap following its switch to proof-of-stake after the Merge:But layer-2 chains like Arbitrum and Optimism are helping Ethereum to share the workload. They use optimistic rollups to roll up hundreds of transactions into one and offload traffic from the Ethereum mainnet to the second layer. This reduces the network load for the first layer and allows for faster transaction processing and cheaper fees by doing the bulk of the computation on the L2 chain.Optimistic rollups derive their name from the optimistic assumption that all transaction data is valid when aggregated into batches for verification on the L1 chain. Both chains use fraud proofs, which you can imagine as tests for the validity of the data. Because these rollups are trustless, transaction finality is instant and the blockchains produce a much higher throughput than Ethereum. The tradeoff is that there is a seven-day challenge window for verifiers to challenge the validity of submitted transactions. There is also a so-called “sequencer,” which orders the transactions before they are submitted to the L1.The main technical difference between the two chains is that Optimism uses single-round fraud proofs while Arbitrum uses multi-round fraud proofs. In normal English, this means Optimism’s method is faster but potentially more expensive due to higher gas fees because it’s executed on the L1. Arbitrum’s way takes more time but is more cost-effective.Moreover, Optimism uses the Ethereum Virtual Machine (EVM), while Arbitrum has its own Arbitrum Virtual Machine (AVM). That means Optimism’s programming language is limited to Solidity. Arbitrum supports all EVM programming languages.