Layer 2 rollup: scaling Ethereum without compromising security

Cheaper Ethereum That Still Settles on Ethereum

A Layer 2 rollup is a separate blockchain that executes transactions off the main Ethereum chain, then periodically posts a compressed summary of those transactions back to Ethereum (the Layer 1). Users get dramatically lower fees and faster confirmation because rollups are not competing for scarce L1 block space, while inheriting Ethereum's security guarantees through the data they post.

There are two main flavors. Optimistic rollups—Arbitrum and Optimism are the largest—assume transactions are valid by default and rely on a challenge window during which anyone can submit fraud proofs. Zero-knowledge (ZK) rollups—zkSync, Starknet, Linea, Scroll—post a cryptographic validity proof with each batch, so correctness is verified mathematically rather than challenged. ZK rollups can finalize faster but are more complex to build.

From a user perspective, an L2 looks like a slightly different network in your wallet. You bridge ETH or tokens over from L1, then transact freely with cents-level fees. Most major DeFi protocols are deployed on the leading L2s, so you can do almost everything you can do on L1 for a fraction of the cost. The main caveats are bridging delays back to L1 (especially with optimistic rollups, which can take a week to finalize withdrawals without using a third-party fast bridge) and varying degrees of decentralization across rollup operators.