Data Availability
Data availability is the assurance that data needed to verify or reconstruct a blockchain or rollup state can actually be obtained.
✦ Key Insight
It is a core security assumption for rollups and modular blockchain systems.
✕ Common Misconceptions
Data availability is not the same as permanent archival storage.
Detailed Explanation
In Practice
Dig Deeper
On-Chain Data
On-chain data is information recorded directly on a blockchain, such as transactions, balances, contract events, and block information.
Layer 2
A Layer 2 is a system built on top of a base blockchain to increase capacity or reduce costs while relying on the underlying chain for some security or settlement.
Rollup
A rollup is a Layer 2 scaling system that executes many transactions away from the base chain and posts compressed data or proofs back to it.
Optimistic Rollup
An optimistic rollup is a Layer 2 design that executes transactions off the base chain and treats posted results as valid unless successfully challenged.
ZK Rollup
A zero-knowledge rollup is a Layer 2 system that batches transactions and uses validity proofs to demonstrate correct state transitions to the base chain.