Layer 2s and rollups
The short answer
Layer-2 networks handle transactions off the main chain and post compressed results back to it, cutting fees while borrowing the main chain's security.
The scaling problem
Every Ethereum nodeNode A computer that keeps a copy of a blockchain and checks that new transactions follow the rules. re-executes every transaction. That’s what makes it trustworthy, and also what limits how many transactions fit in each block. When demand rises, gas feesGas fee The fee you pay to have a transaction processed on Ethereum and similar networks. rise with it.
The layer-2 idea
A layer 2Layer 2 A network built on top of a blockchain that processes transactions more cheaply and settles back to it. network processes transactions on its own, then posts a compressed summary to Ethereum (layer 1). Users get cheaper, faster transactions. Ethereum still acts as the final record and dispute court.
Two kinds of rollups
Optimistic rollups assume batches are valid and allow a challenge window, typically about a week, during which anyone can submit a fraud proof. It’s simple and flexible, but withdrawing directly to Ethereum takes days.
ZK rollups attach a zero-knowledge proofZero-knowledge proof A way to prove something is true without revealing the underlying data. to each batch that mathematically proves it was processed correctly. Ethereum verifies the proof and finality is faster, but the cryptography is complex and proving can be costly.
What to watch
- Sequencers: most rollups rely on a single operator to order transactions today. It can’t steal funds, but it can delay or censor them.
- Upgrade keys: many rollups can still be upgraded by a small council.
- BridgesBridge A service that moves tokens between blockchains, often by locking them on one chain and issuing copies on another.: moving funds between layers and chains adds its own risks.
Rollups are a big reason fees for everyday users fell sharply after 2023.
Last reviewed Oct 3, 2026. Educational content only, not financial advice.