ZK-Rollup
A layer 2 scaling method that bundles many blockchain transactions and proves their validity with zero-knowledge proofs.
A ZK-rollup is a layer 2 scaling system that processes transactions away from a main blockchain, such as Ethereum, then posts a compact summary back to it. The “ZK” stands for zero-knowledge, because the rollup uses a cryptographic proof to show that the bundled transactions were valid without requiring the main chain to recheck every detail. The main chain stores enough data and verifies the proof, so it can inherit much of the security of the underlying blockchain while reducing congestion.
ZK-rollups matter because they can make transfers, swaps, and app interactions faster and cheaper than doing each action directly on the main chain. For example, instead of 1,000 users each paying for a separate Ethereum transaction, a ZK-rollup can combine those actions into one batch and submit a proof that the batch followed the rules. Compared with optimistic rollups, which assume transactions are valid unless challenged, ZK-rollups rely on validity proofs up front.
Other terms in Layer 2 & Scaling
Data Availability
The assurance that the transaction data needed to verify a blockchain or layer 2 network can be accessed by anyone who needs it.
Fraud Proof
A fraud proof is evidence submitted to a blockchain to show that a proposed transaction result or rollup state is invalid.
Layer 2
A Layer 2 is a secondary network or protocol built on top of a blockchain to process transactions faster and cheaper while relying on the main chain for security.
Layer 3
A Layer 3 is an application-specific blockchain layer built on top of a Layer 2 to add customization, scalability, or specialized features.