# ZK-Rollup

> A layer 2 that posts cryptographic proofs back to the main chain to show its batches are valid.

Canonical URL: https://fudfomo.co/glossary/zk-rollup
Source: What The Block! Dictionary v1.0 (last updated 2026-04-25), browsable at https://wtb.fudfomo.co.

## Definition

A zero-knowledge rollup, usually shortened to ZK-rollup, runs transactions on its own network and then attaches a small cryptographic proof showing they all followed the rules. The main chain only has to verify the proof, which is much cheaper than re-running the transactions.

Because the proof is checked instantly, withdrawals are much faster than with optimistic rollups. The maths is more complex, which is why ZK technology has taken longer to mature.

## Related terms

- [Rollup](https://fudfomo.co/glossary/rollup): A type of layer 2 that bundles many transactions together and writes a summary back to the main chain.
- [Layer 2](https://fudfomo.co/glossary/layer-2): A faster, cheaper network built on top of a layer 1 like Ethereum. Borrows the main chain's security.
- [Validity Proof](https://fudfomo.co/glossary/validity-proof): A cryptographic proof that a batch of transactions on a ZK-rollup followed all the rules.
- [Ethereum](https://fudfomo.co/glossary/ethereum): A blockchain that lets developers build apps and issue tokens. Often called a programmable money platform.

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