How Does the “Fraud Proof” Mechanism Work in an Optimistic Rollup?

An Optimistic Rollup assumes all transactions processed off-chain are valid ("optimistic") and publishes the transaction data to the main chain. A "fraud proof" is a mechanism that allows any network participant to challenge the validity of a rolled-up block during a specific time window.

If a challenge is successful, the fraudulent block is reverted, and the validator who submitted the incorrect state is penalized (slashed). This system ensures security without requiring complex, constant on-chain computation.