Layer 2

What Is Layer 2?

Layer 2 (L2) refers to a secondary framework or protocol built on top of an existing blockchain -- known as Layer 1 (L1) -- to improve its scalability, throughput, and cost-efficiency. Rather than processing every transaction directly on the main chain, L2 solutions handle transactions off-chain or in compressed batches, then post proofs or summaries back to the base layer for final settlement.

Layer 2 solutions have become one of the most important infrastructure developments in crypto, enabling decentralized applications to serve millions of users without being bottlenecked by the limited capacity of their underlying L1 networks.

Why Layer 2 Matters

Networks like Ethereum can process roughly 15-30 transactions per second on their base layer. During periods of high demand -- such as popular NFT mints, token launches, or market volatility -- this limited throughput drives gas fees to levels that make small transactions economically unviable. A simple token swap might cost $50 or more in gas during peak congestion.

Layer 2 solutions address this by moving the bulk of computation off the main chain while still inheriting its security guarantees. The result is dramatically lower fees (often pennies instead of dollars) and significantly faster transaction confirmation times, all without sacrificing the decentralization or security properties of the underlying L1.

How Layer 2 Solutions Work

Rollups

Rollups are the dominant L2 scaling strategy today. They bundle hundreds or even thousands of transactions into a single compressed batch, which is then submitted to the L1 as one transaction. This amortizes the cost of L1 block space across all the bundled transactions, reducing per-transaction fees by orders of magnitude.

There are two main types of rollups:

Optimistic rollups assume all transactions in a batch are valid by default. They include a challenge period (typically seven days) during which anyone can submit a fraud proof if they detect an invalid transaction. Arbitrum and Optimism are the most prominent optimistic rollup networks, collectively hosting billions of dollars in DeFi activity.

Zero-knowledge rollups (ZK rollups) use cryptographic validity proofs to mathematically verify that every transaction in a batch is correct. This eliminates the need for a challenge period, enabling faster finality when bridging assets back to L1. zkSync, StarkNet, and Polygon zkEVM are leading ZK rollup implementations.

Other Approaches

Beyond rollups, other L2 approaches include state channels, which allow two parties to conduct numerous transactions off-chain and only settle the final state on-chain, and sidechains, which run their own consensus mechanisms but periodically checkpoint to the main chain. However, rollups have largely superseded these earlier designs for general-purpose scaling.

Layer 2 and DeFi

The rise of Layer 2 networks has profoundly impacted DeFi. Major lending protocols like Aave and Compound have deployed on multiple L2 networks, giving borrowers and lenders access to the same functionality at a fraction of the cost. Liquidity on L2s has grown rapidly, with total value locked across rollup networks reaching tens of billions of dollars.

For DeFi users, L2s mean that actions like supplying collateral, borrowing stablecoins, or adjusting positions no longer require paying prohibitive gas fees. This makes active position management more practical and opens DeFi to users with smaller portfolio sizes who were previously priced out by L1 costs. Some aggregators support lending across multiple L2 networks including BASE, Arbitrum, Optimism, and Polygon, letting borrowers compare rates and access the best terms regardless of which chain offers them.

Choosing a Layer 2 Network

When selecting an L2, users should consider factors such as transaction fees, speed of finality, the availability of their preferred DeFi protocols, liquidity depth, and the ease of bridging assets from L1. Each L2 network has its own ecosystem of applications, and liquidity can vary significantly between them. Comparing options across multiple networks ensures borrowers and lenders find the most competitive rates and deepest markets for their needs.