Ethereum Layer-2 Fees: Why Rollups Are So Much Cheaper
What a rollup is
A rollup is a separate chain that executes transactions on its own and periodically posts the data needed to reconstruct its state to Ethereum mainnet. Because thousands of rollup transactions share the cost of a single mainnet posting, each user pays only a tiny slice of that cost plus a small execution fee on the rollup itself. Optimistic rollups such as Arbitrum, Optimism and Base assume posted batches are valid unless challenged. Zero-knowledge rollups such as zkSync, Scroll and Linea attach validity proofs.
The two parts of a layer-2 fee
- L2 execution fee. The rollup's own gas price for running your transaction. It is usually extremely low because rollup blocks have plenty of room.
- L1 data fee. Your share of the cost of publishing the batch data on Ethereum. This part tracks mainnet conditions, which is why L2 fees can still rise during a mainnet spike.
What EIP-4844 and blobs changed
The Dencun upgrade in March 2024 introduced "blob" transactions: a separate, cheaper data lane intended specifically for rollup data, with its own fee market. Before blobs, rollups stored data in regular calldata and competed with every other mainnet transaction. After blobs, the L1 data component of L2 fees dropped dramatically, and typical L2 transfers and swaps now cost fractions of a cent.
When mainnet still makes sense
- Large transfers where maximum settlement security on Ethereum itself matters.
- Protocols or assets that exist only on mainnet.
- Moving funds into or out of rollups through the canonical bridge, which requires a mainnet transaction. See the bridge cost page.
Trade-offs to keep in mind
Withdrawals from optimistic rollups through the canonical bridge take about a week because of the challenge window. Third-party bridges are faster but add counterparty and smart-contract risk. Many rollups still rely on a centralized sequencer to order transactions. None of this makes rollups unsafe for everyday use, but it is worth understanding before you move large amounts.
Bottom line
If the app you need runs on an L2, using it is the most effective way to cut fees. Keep an eye on mainnet gas with the GasNow tracker when you bridge, because the bridge transaction itself is paid at mainnet prices.
Frequently asked questions
Why are layer-2 fees so low?
Rollups batch many transactions into one mainnet posting, and since EIP-4844 that data goes into cheaper blob space, so each user pays a tiny share.
Can layer-2 fees spike?
Yes, but far less than mainnet. The L1 data component follows Ethereum demand, and the rollup's own fee can rise during heavy local activity.