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What is a ZK-rollup?
A ZK-rollup is a layer 2 network that bundles transactions, executes them off Ethereum, and posts a summary with a cryptographic validity proof. A contract on Ethereum checks the proof and accepts the new balances only if the proof is correct.
What it means for you
Because each batch is proven, withdrawals to Ethereum do not wait through a challenge period; they complete once the proof is verified. The operator that orders transactions can still delay or censor them, and ethereum.org describes an escape hatch: submitting the transaction directly to the rollup contract on mainnet.
How it works
The rollup's state is a Merkle tree whose root is stored in a contract on Ethereum. The operator executes a batch off-chain, then submits the new root, a compact summary of the changes, and a validity proof; the verifier contract updates the root only if the proof checks. Proofs are usually SNARKs, which are small and quick to verify but rely on a one-time setup ceremony, or STARKs, which need no setup but are larger and cost more to verify. Proving general EVM computation is harder and more resource-intensive than proving simple transfers.
Source: ethereum.org: Zero-knowledge rollups · checked 4 October 2026
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