What are layer 2 networks?
Cheaper, faster networks that lean on a main blockchain for security.
A layer 2 is a separate network that processes transactions cheaply and quickly, then posts a summary back to a main blockchain (layer 1) such as Ethereum, borrowing its security. Popular examples include Arbitrum, Optimism, Base and zkSync.
Why they exist
A main blockchain can only fit so many transactions in each block. When demand is high, fees rise. Layer 2s handle the bulk of transactions off the main chain and post compressed results back to it, so each user pays a fraction of the cost.
Blockchain designers often talk about a trilemma: it's hard for one network to be highly decentralized, highly secure and very fast all at once. Layer 2s are Ethereum's answer: keep the base layer secure and decentralized, and do the high-speed work on top.
Two kinds of rollup
- Optimistic rollups (Arbitrum, Optimism, Base) assume batches are valid unless someone proves fraud during a challenge window. Withdrawing straight back to Ethereum through the official bridge can take about a week.
- Zero-knowledge (ZK) rollups (zkSync, Starknet, Linea) post a mathematical proof that each batch is valid, so withdrawals can be faster.
What to watch out for
ETH on Base is not on the same network as ETH on Ethereum. Sending between them needs a bridge or an exchange that supports both. Picking the wrong network when you send is one of the most common costly mistakes. Read what happens if you send to the wrong network.
- Bridges, which move tokens between networks, have been some of the biggest hacking targets in crypto.
- Training wheels: many layer 2s still rely on a small group that can upgrade or pause the system, so they aren't yet as decentralized as Ethereum itself.
Frequently asked questions
Is Base a separate blockchain?
Base is a layer 2 built on Ethereum. It has its own network, so you must choose Base specifically when sending or withdrawing to it.
Are layer 2s safe?
They inherit much of Ethereum's security, but each has its own risks, including bridge bugs and upgrade controls. Check the network carefully before moving large amounts.
Do I need ETH on a layer 2?
On most Ethereum layer 2s, yes: fees are paid in ETH on that layer 2.
Where to next
Sources
Written for beginners and checked against the sources listed. Last reviewed October 26, 2026. This page is educational and is not financial, tax or legal advice. How we write and check pages.