Glossary · Z
zkRollup
A Layer 2 scaling solution that batches hundreds of transactions off-chain and submits a cryptographic proof (zero-knowledge proof) to Ethereum, verifying the validity of all transactions without revealing their contents. zkRollups offer Ethereum-level security with drastically lower fees. zkSync Era and Polygon zkEVM are leading zkRollup networks.
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How zkRollup works in practice
A zk-rollup proves correctness cryptographically with every batch rather than relying on someone to challenge it. Validity is established up front, so there is no dispute window and withdrawals finalise as soon as a proof is verified.
Worked example
The rollup submits a validity proof alongside its batch. Ethereum verifies the proof, which is far cheaper than re-executing the transactions, and the state is final immediately.
Figures are illustrative and chosen to be checkable, not live market data.
The mistake that costs people money
Proving is computationally expensive and the systems are newer, so a bug in the proving circuit is a real if low-probability risk. Many deployments also retain upgrade keys, which matters more than the cryptography in practice.
zkRollup: common questions
- What is zkRollup?
- A Layer 2 scaling solution that batches hundreds of transactions off-chain and submits a cryptographic proof (zero-knowledge proof) to Ethereum, verifying the validity of all transactions without revealing their contents. zkRollups offer Ethereum-level security with drastically lower fees. zkSync Era and Polygon zkEVM are leading zkRollup networks.
- How does zkRollup work in practice?
- A zk-rollup proves correctness cryptographically with every batch rather than relying on someone to challenge it. Validity is established up front, so there is no dispute window and withdrawals finalise as soon as a proof is verified.
- Can you give an example of zkRollup?
- The rollup submits a validity proof alongside its batch. Ethereum verifies the proof, which is far cheaper than re-executing the transactions, and the state is final immediately.
- What do people get wrong about zkRollup?
- Proving is computationally expensive and the systems are newer, so a bug in the proving circuit is a real if low-probability risk. Many deployments also retain upgrade keys, which matters more than the cryptography in practice.