What are rollups and how do they scale Ethereum?
A deeper look at optimistic and zero-knowledge rollups — how they cut fees, inherit Ethereum's security, and differ from each other.
Last reviewed August 7, 2026
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Rollups are the centrepiece of Ethereum's scaling strategy. They execute transactions off the congested base layer, then post compressed data back to Ethereum for security. Understanding rollups is key to understanding where Ethereum activity — and value — is heading.
What is a rollup?
A rollup is a layer-2 chain that batches many transactions together, executes them off-chain, and submits a compressed summary to Ethereum. Users get low fees and fast confirmation while ultimately relying on Ethereum to settle disputes and guarantee data.
Optimistic vs zero-knowledge rollups
The two main designs differ in how they prove correctness. Optimistic rollups assume transactions are valid and allow a challenge period to dispute fraud. Zero-knowledge rollups generate a cryptographic proof that the batch is valid, enabling faster finality without a challenge window.
How do rollups cut fees?
- They spread the cost of settling to Ethereum across many bundled transactions
- Compression reduces the data each transaction must post
- Dedicated data 'blobs' lowered the cost of posting rollup data dramatically
- Competition between rollups pushes fees toward the cost of data
Why do rollups inherit Ethereum's security?
Because rollups post their transaction data and proofs to Ethereum, the base layer can verify or challenge them. This anchoring means a rollup does not need its own trusted validator set for settlement — it borrows Ethereum's, which is the source of its security.
What rollups mean for ETH
Rollups move execution — and its fees — up the stack, which is great for users but reduces base-layer fee burn. The long-run question is how much value accrues to ETH as the settlement and data-availability layer beneath a growing rollup ecosystem. See our Ethereum market page for live data.
Frequently asked
What is the difference between optimistic and ZK rollups?
Optimistic rollups assume validity and allow a dispute window; zero-knowledge rollups submit a cryptographic proof of validity, enabling faster finality without a challenge period.
Do rollups have their own security?
For settlement they inherit Ethereum's security by posting data and proofs to it, though they add bridge and sequencer considerations of their own.
Why did rollup fees fall so much?
A base-layer upgrade added dedicated data space (blobs) for rollups, sharply cutting the cost of posting their data to Ethereum.
Lauren Bennett is a Senior Bitcoin Analyst at Crypto Almanac Daily, specializing in Bitcoin market structure, on-chain analytics, mining economics, institutional adoption, spot ETF developments, and macroeconomic trends shaping digital assets. Her reporting focuses on translating complex blockchain data into clear, data-driven insights for investors, industry professionals, and readers following the evolution of the Bitcoin ecosystem. Lauren regularly analyzes network activity, miner behavior, liquidity trends, exchange flows, and the impact of monetary policy on digital asset markets. Before joining Crypto Almanac Daily, she covered financial markets and emerging technologies, developing expertise in blockchain infrastructure and digital asset research. Her work emphasizes factual reporting, transparent analysis, and long-term market fundamentals rather than short-term speculation. At Crypto Almanac Daily, Lauren contributes daily news coverage, in-depth market analysis, educational explainers, and feature articles that help readers better understand Bitcoin's role in the global financial system and the rapidly evolving digital asset economy.
This guide is educational and general in nature. It is not financial, investment, legal or tax advice, and it does not account for your circumstances. Crypto assets are volatile and you can lose the money you put in. See our editorial policy and methodology.
