Crypto glossary
Rollup
A rollup is a layer 2 that executes transactions off-chain, bundles them together and posts the data to a base blockchain such as Ethereum for security.
A rollup processes hundreds or thousands of transactions outside the main chain, compresses them into a batch and publishes it on the layer 1. Because the data sits on the base chain, anyone can reconstruct the rollup's state, and users can in principle exit even if the operator disappears.
There are two main types. Optimistic rollups, such as Arbitrum, Optimism and Base, assume batches are valid and allow a challenge period, typically about seven days, during which anyone can submit a fraud proof. ZK rollups, such as zkSync, Starknet, Scroll and Linea, attach a zero-knowledge validity proof to each batch, so withdrawals can finalize faster.
Rollups are Ethereum's main scaling path. Their maturity is often rated in stages, depending on whether fraud or validity proofs are live and how much control the team keeps over upgrades and the sequencer.
Example
Withdrawing ETH from Optimism to Ethereum through the official bridge takes about a week because of the fraud-proof window, while third-party bridges offer faster exits for a fee.
Related terms
Latest articles on Rollup
- The 2026 Layer 2 Shutdowns Confirm Rollup Expansion Exceeded Real Demand
- DogeOS Brings ZK-Rollups, EVM Smart Contracts and DeFi to Dogecoin
- Ethereum Hits Record Blob Usage as Rollup Demand Reaches New High
- Ethereum Can’t Scale Alone — Here’s How Rollups Are Changing the Network
- GnosisDAO Approves Gnosis Chain’s Move to a ZK‑Proven EEZ Rollup
