# What's a rollup?

Rollups work by bundling or ‘rolling up’ off-chain transactions into a smaller transaction that gets sent to Layer 1. By sending the transactions back to Layer 1, rollups inherit the security and finality of the Ethereum blockchain.

There are two types of rollup: **Zero knowledge (ZK) and Optimistic.**

Determining if ZK-rollups or optimistic rollups are superior depends on the specific needs of a blockchain network. ZK-rollups provide enhanced security and privacy through zero-knowledge proofs, allowing transaction verification without revealing details and reducing data storage requirements.

Optimistic rollups can technically offer higher scalability, processing more transactions per second, and are easier to implement without needing complex zero-knowledge proofs. Hence, the choice depends on network goals, and a hybrid approach may combine the best features of both rollups.
