What Is the Difference between an Optimistic Rollup and a ZK-Rollup?

Both are Layer-2 scaling solutions, but they differ in their security model. Optimistic Rollups assume transactions are valid by default and use a "fraud proof" system, allowing a challenge period for invalid transactions.

ZK-Rollups (Zero-Knowledge) prove the validity of all transactions cryptographically off-chain using complex math (zero-knowledge proofs) before posting a single summary to Layer-1. ZK-Rollups have faster finality.

How Do ZK-Rollups Inherently Offer Better Privacy against Front-Running than Optimistic Rollups?
What Is the Trade-off in Computational Complexity between the Two Rollup Types?
What Layer 2 Solution Eliminates the Need for a Long Withdrawal Period?
What Is the Difference between an “Optimistic Rollup” and a “ZK-Rollup”?
What Are the Security Trade-Offs between Optimistic Rollups and ZK-Rollups for Financial Applications?
What Is the Minimum Length of a Typical Challenge Period in an Optimistic Rollup?
How Do Fraud Proofs in Optimistic Rollups Work to Secure Funds?
How Does the “Fraud Proof” Mechanism Work in an Optimistic Rollup?

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