Layer 2 (L2)
Layer 2 (L2): A layer 2 (L2) is a network built on top of an existing blockchain, called the layer 1, to make transactions faster and cheaper. It processes transactions away from the main chain, then posts the results or proofs back to it, so it relies on the layer 1 for much of its security.
How layer 2 networks work: rollups
Most Ethereum layer 2s are rollups. They bundle many transactions together and post compressed data back to Ethereum. Optimistic rollups assume transactions are valid unless someone challenges them within a set window. Zero knowledge (ZK) rollups post a cryptographic proof that each batch is valid.
Examples of layer 2 networks
Arbitrum, Optimism and Base are optimistic rollups on Ethereum, while zkSync uses zero knowledge proofs. On Bitcoin, the Lightning Network is a layer 2 built for fast, low fee payments.
Layer 2 trade offs
Fees are much lower, but moving funds between a layer 2 and the main chain uses a bridge, and withdrawals through an optimistic rollup’s own bridge can take about a week. Many layer 2s still rely on a single operator for some functions, so decentralisation varies.
Frequently asked questions
Is a layer 2 safer than a layer 1?
Not usually. A layer 2 adds its own smart contract and operator risks on top of the layer 1 it settles to.
Do I need a different wallet for layer 2?
Usually not. Most Ethereum wallets support the major layer 2 networks. You switch network in the wallet and pay fees on that network.