GlossaryAdvanced
Optimistic Rollup
A rollup design that assumes submitted transactions are valid by default, relying on a challenge window for anyone to dispute incorrect ones.
An optimistic rollup is a type of rollup that assumes the transactions it submits to the base chain are valid by default, without requiring an immediate cryptographic proof of correctness.
Instead, it provides a challenge window — a set period during which anyone can submit a fraud proof disputing an incorrect batch of transactions. This trades faster, cheaper transaction processing for a withdrawal delay to the base chain, since funds generally can't be considered fully final until the challenge window has passed.
Examples
- An optimistic rollup's challenge window is why withdrawing funds back to the base chain typically takes longer than on a validity-proof-based (ZK) rollup.
- A fraud proof submitted during an optimistic rollup's challenge window can reverse an incorrect batch of transactions before it becomes final.