Scroll is a zkEVM-based zkRollup on Ethereum that enables native compatibility for existing Ethereum applications and tools.
UniFi'd Blockchain Ecosystem
Layer 2 scaling solution for NFTs
StarkWare is a ethereum layer-2 scaling protocol and one of main zk-rollup solutions. Starkware builds StarkNet( a permissionless decentralized ZK-Rollup) and StarkEx(a standalone permissioned Validity-Rollup), both layer-2 scaling solutions for Ethereum using zero-knowledge rollup technology.
Bitcoin Economic Layer
Taiko is a decentralized Ethereum-equivalent ZK-EVM and general-purpose ZK-Rollup. Its purpose is to allow developers and users of dApps developed for Ethereum L1 to be used on Taiko without any changes.