Zero-knowledge rollups (ZK rollups) bundle transactions off-chain and use cryptographic proofs to verify them on Ethereum. StarkNet and zkSync are top examples, cutting costs and boosting speed while ensuring security. Unlike optimistic rollups, they don’t require long withdrawal times since validity proofs confirm transactions instantly. ZK rollups also enhance privacy by revealing only essential data, making them ideal for DeFi, payments, and secure dApps.