Overview
A rollup is a Layer 2 scaling solution that bundles, or rolls up, multiple transactions into a single batch and posts compressed data to the main chain. By executing transactions off-chain and publishing a summary to Ethereum, rollups drastically reduce the cost and congestion burden on Layer 1 while inheriting its security. Rollups are the dominant scaling approach for Ethereum as of 2026.
How It Works
A rollup executes transactions on its own chain, then posts either the full transaction data (optimistic rollups) or a cryptographic validity proof (ZK-rollups) to Ethereum. The main chain verifies the posted data or proof, ensuring the rollup cannot cheat. Users bridge assets into the rollup, transact at low fees, and withdraw back to Layer 1 through the bridge, with a delay that depends on the rollup's fraud-proof or proof-verification design.
Why It Matters
Rollups multiply the throughput of the underlying chain while keeping its security model. They are the path Ethereum chose for mass adoption, and they create a vibrant ecosystem of specialized chains. Their differences in finality time, withdrawal latency, and upgrade authority matter for developers and users choosing where to build.
Related Concepts
Rollups split into Optimistic Rollups, which use fraud proofs, and ZK-Rollups, which use validity proofs. Both connect to Layer 1 through Bridges and fit into the broader Modular Blockchain stack.