What is a ZK Rollup?

How ZK Rollups Work

1. Transaction Aggregation:
   • Transactions are processed and grouped (batched) off-chain by the rollup.
   • These batches consist of multiple user transactions submitted to the rollup via sequencers or validators12.
2. Proof Generation:
   • Instead of submitting each individual transaction to the layer 1 blockchain, the rollup generates a single cryptographic proof called a validity proof (using zero-knowledge proofs such as zk-SNARKs or zk-STARKs) for the entire batch1324+1.
   • This proof certifies that all transactions in the batch are valid.
3. Onchain Verification:
   • The batch of transactions and the validity proof are submitted to the layer 1 blockchain.
   • The blockchain verifies just this single proof, drastically reducing computational and storage requirements on the main chain, and then finalizes the batch125.

Key Features and Benefits

• Scalability: By batching many transactions into one proof, ZK rollups support much higher transaction throughput and alleviate congestion on the base layer127.
• Lower Fees: Because only proof data is submitted onchain (rather than every transaction), users typically benefit from lower fees compared to layer 1 transactions and even other rollup types87.
• Security: The rollup inherits the full security of the underlying blockchain, since any attempt to submit invalid proofs will be rejected by the base chain12.
• Faster Finality: Validity proofs are verified immediately without an extended dispute period (unlike optimistic rollups), resulting in faster transaction confirmations29.

ZK Rollups & Validity Proofs

• ZK rollups rely on "validity proofs," which guarantee transaction correctness but don't always include privacy features (not all ZK rollups use zero-knowledge properties strictly for privacy)311.
• The two major cryptographic systems used in ZK rollups are zk-SNARKs (succinct, efficient proofs) and zk-STARKs (transparent, post-quantum secure proofs)312.

Ecosystem & Adoption

Summary Table