Optimism

zkSync is Ethereum’s most user-centric ZK rollup. Unlike any other scaling approach, ZK rollup has no upper bound on the value it can securely handle in L2. Unlike optimistic rollups, all assets can be moved capital-efficiently and fast between ZK rollup and L1. zkSync has the lowest real tx costs across all existing and planned rollups. zkSync also supports meta-transactions, instant confirmations with economic finality, low-cost privacy, and more. Ease and fun of development are at the core of zkSync design. Integrate payments and atomic swaps in a few lines of code. Develop type-safe, functional style smart contracts on Zinc: a Rust-based framework. Deploy your existing EVM codebase with minimum modifications.

Next generation layer 2 for Ethereum dApps. Use your favorite tools and scale your dApp at the lowest cost. An aggregator plays the same role that a node plays in Ethereum. Client software can do remote procedure calls (RPCs) to an aggregator, using the standard API, to interact with an Arbitrum chain. The aggregator will then make calls to the EthBridge and produce transaction results to the client, just as an Ethereum node would. Most clients will use an aggregator to submit their transactions to an Arbitrum chain, although this is not required. There is no limit on how many aggregators can exist, nor on who can be an aggregator. To improve efficiency, aggregators will usually package together multiple client transactions into a single message to be submitted to the Arbitrum chain. Arbitrum also supports a privileged Sequencer that can order transactions and give low latency transaction receipts.