Understanding the distinctions of Ethereum L2 At the end of the year, following the Ethereum Fusaka upgrade, Ethereum L2s are likely to gain significant attention. The distinctions of Ethereum L2 can be broadly categorized into two main aspects: (1) Verification method: Optimistic / ZK (2) DA location: Ethereum / external DA (EigenDA, Celestia..) Accordingly, the types of Ethereum L2 can be divided into the following four categories: 1. Optimistic Rollup - Verification method = Optimistic - DA = Ethereum L1 L2 data is rolled up directly to Ethereum L1, and settlements are made on Ethereum. After optimistic settlement without separate verification on L1, there is a challenge period of 7 days. Base, Optimism, @arbitrum, etc. fall under this category. 2. ZK Rollup - Verification method = ZK - DA = Ethereum L1 L2 data is rolled up directly to Ethereum L1, and settlements are made on Ethereum. ZK proofs are rolled up to Ethereum to verify the proofs through Ethereum contracts. Verification is completed simultaneously with the rollup. ZKsync, Starknet, @katana, etc. fall under this category. 3. Optimium - Verification method = Optimistic - DA = external DA (EigenDA/Celestia..) L2 data is stored in external DA solutions or independently, not on Ethereum. Only settlements are made on the Ethereum mainnet, using the optimistic verification method similar to Optimistic rollups. Arbitrum Nova, etc. fall under this category. It can be considered the least secure L2. 4. Validium - Verification method = ZK - DA = external DA (EigenDA/Celestia..) L2 data is stored in external DA solutions or independently, not on Ethereum. Settlements are made on the Ethereum mainnet, and ZK proofs are verified through Ethereum mainnet contracts, similar to ZK rollups. Sophon, Lens, @Mantle_Official, and the soon-to-be-released @megaeth_labs fall under this category. At this point, there are projects that claim to be ZK rollups simply because they use ZK for verification, but if they do not use Ethereum for DA, then that is Validium, not ZK rollup. If someone claims that MegaETH is a ZK rollup, you can now say, Ah, that's not a ZK rollup!