Layer 2

A Layer 2 is a network built on top of a base blockchain (the “Layer 1”) to raise transaction throughput and cut fees, while still relying on the base chain for final security.

How it works

Layer 2s move the bulk of transaction processing off the main chain, then post compressed proofs or data back to it. Rollups, the most common approach, batch many transactions together and submit a single summary to Layer 1; “optimistic” rollups assume batches are valid unless challenged, while “zero-knowledge” rollups attach a cryptographic proof of validity. Either way, users get cheaper, faster transactions backed by the base chain.

Why it matters

Scaling is one of crypto’s central challenges: secure, decentralized base chains have limited capacity. Layer 2s let a network serve far more users without sacrificing the underlying security, which is why much of Ethereum’s activity now happens on them.

Example

Rollup networks that settle to Ethereum let users transact for a fraction of mainnet gas fees.

Layer 2: Frequently Asked Questions

What is the difference between optimistic and zero-knowledge rollups?

Both batch many transactions and settle to Layer 1, but they prove validity differently. Optimistic rollups assume batches are valid unless someone challenges them within a dispute window. Zero-knowledge rollups attach a cryptographic proof that the batch is correct, so it can be verified immediately. The trade-off is between challenge delays and proof complexity.

Are Layer 2 networks as secure as the base chain?

Layer 2s inherit much of their security from the Layer 1 they settle to, since transaction data or proofs are posted back to it. However, they add their own components, such as sequencers, bridges and proof systems, which introduce extra trust assumptions and potential failure points. Security therefore depends on both the base chain and the specific Layer 2 design.

Why do transactions cost less on a Layer 2?

Layer 2s move most processing off the main chain and compress many transactions into a single summary posted to Layer 1. Because the expensive base-chain space is shared across the whole batch, the cost per individual transaction drops sharply. Users get faster, cheaper transactions while the batch's data or proof still anchors security to the base chain.

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