Ethereum Layer 2 Networks Explained
Why Layer 2 networks exist, how Arbitrum, Base, and Optimism work, and how to use them to pay a fraction of mainnet gas fees.
Why Layer 2 Networks Exist
Ethereum’s main network can only process about 15-34 transactions per second. During busy periods, everyone competes to get their transaction included in the next block, which pushes fees up. In 2021, a single Ethereum swap could cost $50-200 in gas fees.
Layer 2 networks solve this by moving most transaction processing off the main Ethereum chain. They bundle thousands of transactions together, process them on a faster network, and then post a compressed summary back to Ethereum. The result: transactions that take milliseconds and cost fractions of a cent, while still inheriting Ethereum’s security.
How They Work
Every Layer 2 is built on a fundamental idea: use Ethereum as a settlement layer rather than an execution layer.
- You send a transaction on the L2 network
- The L2 processes it near-instantly
- Periodically, the L2 compresses thousands of transactions into a small batch
- That compressed batch gets posted to Ethereum mainnet as a single transaction
- The Ethereum blockchain serves as the final record, guaranteeing security
Your assets are technically secured by Ethereum at all times. The L2 is just a faster lane.
Optimistic vs. ZK Rollups
There are two main flavors of Layer 2. Both achieve the same goal, but differently.
| Type | How it works | Fraud protection | Withdrawal time |
|---|---|---|---|
| Optimistic Rollup | Assumes transactions are valid unless challenged | 7-day challenge window | ~7 days without a bridge |
| ZK Rollup | Generates a cryptographic proof that all transactions are valid | Mathematically proven | Minutes to hours |
Optimistic rollups (Arbitrum, Base, OP Mainnet) are easier to build on because they run the same Ethereum code. ZK rollups (zkSync Era, Scroll, Starknet) are more complex but offer faster withdrawals.
For most users, the difference is invisible day-to-day. Both cost fractions of a cent per transaction.
The Major Networks
These are the networks you are most likely to encounter:
| Network | Type | Developed By | Key Strength |
|---|---|---|---|
| Arbitrum One | Optimistic | Offchain Labs | Largest DeFi ecosystem by TVL |
| Base | Optimistic | Coinbase | Easy onboarding from Coinbase app |
| OP Mainnet | Optimistic | OP Labs | ”Superchain” ecosystem, OP Stack |
| zkSync Era | ZK | Matter Labs | Fast finality, ZK security |
| Scroll | ZK | Scroll Foundation | EVM-compatible ZK rollup |
According to L2Beat, which tracks rollup security and activity, these networks collectively hold tens of billions of dollars in bridged assets.
How the Dencun Upgrade Changed Everything
Before March 2024, Layer 2 networks had to post their transaction data to Ethereum in a format that was expensive to store. The Dencun upgrade introduced a new data type called “blobs” (EIP-4844) specifically for this purpose.
Blobs are temporary, cheaper storage slots on Ethereum that L2s use to post their data. They get deleted after about 18 days, since that is all that is needed for fraud proofs.
The impact was immediate. According to data from L2Fees.info, typical transaction costs on major L2s dropped from $0.05-0.50 to $0.001-0.01 overnight. Some transactions on Base and Arbitrum now cost less than a hundredth of a cent during quiet periods.
This is why 2024-2026 marks a turning point: Ethereum is finally affordable for everyday use, just via its L2 layer.
Getting Started: Bridging to an L2
To use a Layer 2, you need to move ETH from Ethereum mainnet to the L2. This is called “bridging.”
The most beginner-friendly paths:
Option 1: Buy directly onto an L2
Coinbase lets you withdraw ETH directly to Base at no extra cost. If you buy ETH on Coinbase and withdraw to Base, you skip bridging entirely.
Option 2: Use the official bridge
Each network has an official bridge:
Connect your wallet, choose an amount to bridge, and confirm. The ETH arrives on the L2 within a few minutes.
Option 3: Use a third-party bridge
Services like Across and Stargate offer faster bridging between different L2s and reduce the 7-day withdrawal delay of native bridges.
Is My Money Safe on an L2?
This is the right question to ask. L2 security is real but has nuances.
What is secure: Your assets are backed by Ethereum. If an L2 completely shut down, you could always withdraw to mainnet using the smart contracts on Ethereum.
What is not fully secure yet: Most major L2s still have some level of trusted “sequencer” control, meaning one party orders transactions. L2Beat rates each network’s decentralization and security posture on a scale from Stage 0 to Stage 2. As of 2026, most major networks are at Stage 1.
Smart contract risk: Bugs in the L2 bridge contracts could theoretically allow funds to be drained. Each major L2 has been audited, but this risk is real.
For meaningful amounts, check the L2Beat security page for the network you plan to use. It shows exactly which security assumptions you are trusting.
Gas Still Exists on L2s
A common misconception: “L2 transactions are free.” They are not. You still pay gas fees on an L2, but in ETH, and at a fraction of mainnet prices.
You need a small amount of ETH on whatever L2 you are using to pay these fees. The ETH does not need to come from mainnet; you can buy it directly onto an L2 via Coinbase or other exchanges that support direct L2 withdrawals.
The Bottom Line
Layer 2 networks make Ethereum practical for everyday use. They give you the same security guarantees as the main chain at costs that are 100x cheaper. For most things you want to do on Ethereum, from DeFi to sending tokens to using apps, an L2 is the right place to do it.
Start with Base if you already use Coinbase. Start with Arbitrum if you want the broadest DeFi access. Both are battle-tested and beginner-friendly.
This is not investment advice.
Related Guides
- What is Ethereum? — Understand the base layer first
- How to Buy Ethereum — Get ETH before you bridge
- Crypto Wallets Explained — Set up a wallet to use L2s
- Proof of Stake Explained — How Ethereum’s consensus works