# Rollup

*Crypto & Digital Assets — Finicade finance glossary*

A rollup batches many transactions into one posting on the main chain. Optimistic rollups assume the batch is valid and allow a challenge window, which is why withdrawals can take days. Zero-knowledge rollups post a cryptographic proof of correctness instead, giving faster finality at a higher computational cost. The two designs are converging as proving costs fall.

**Also known as:** optimistic rollup, zk-rollup, zero-knowledge rollup

**Related terms:** [Layer 2](https://finicade.com/glossary/layer-2), [Ethereum](https://finicade.com/glossary/ethereum), [Gas Fee](https://finicade.com/glossary/gas-fee), [Bridge](https://finicade.com/glossary/bridge), [Blockchain](https://finicade.com/glossary/blockchain)

Source: https://finicade.com/glossary/rollup