Ethereum Layer 2s: Arbitrum, Base, Optimism and the Rollup Era
Why L2s exist, how they reduce fees, and how they relate to the Ethereum mainnet.
Ethereum's base layer, often called L1, processes every transaction in a single global queue. When demand spikes, users bid up gas fees to get their transactions included. Layer 2 networks — commonly called rollups — were designed to relieve that congestion without changing Ethereum itself.
A rollup executes transactions on its own network, then periodically posts a compressed summary and cryptographic proof back to Ethereum. Users get much lower fees and much faster confirmations, while Ethereum L1 remains the ultimate source of truth.
Arbitrum, Base, and Optimism are three of the most widely used rollups. Each has its own fee market, its own set of applications, and its own bridge for moving assets to and from Ethereum. From a user's perspective, they feel like separate networks that happen to inherit Ethereum's security.
For someone learning the ecosystem, the practical takeaway is simple: an ETH balance on Arbitrum is not the same as an ETH balance on Optimism or on mainnet, even though the underlying asset is called ether in all three places. Always check which network your wallet is connected to before sending.