Data Availability
Data availability is the assurance that all network participants can access and verify the transaction data necessary to settle the state of a blockchain.
Key Differences: Data Availability (Proof of publication) vs Data Storage (Long-term archival). Core Mechanisms: 1. Erasure Coding. 2. DAS Sampling. 3. Commitments (KZG/Fraud Proofs). Impact: Directly dictates the maximum throughput (TPS) of rollups and the cost of on-chain transactions.
graph LR
Center["Data Availability"]:::main
Rel_evm_opcode_analysis["evm-opcode-analysis"]:::related -.-> Center
click Rel_evm_opcode_analysis "/terms/evm-opcode-analysis"
Rel_evm_optimization["evm-optimization"]:::related -.-> Center
click Rel_evm_optimization "/terms/evm-optimization"
Rel_evm_specification["evm-specification"]:::related -.-> Center
click Rel_evm_specification "/terms/evm-specification"
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🧒 Explain Like I'm 5
Imagine a town hall where everyone votes. [Data availability](/en/terms/data-availability) is like the requirement that the final vote count must be posted on the public scoreboard FOR EVERYONE TO SEE. If the mayor just says 'I won', but hides the list of who voted for whom, you have a 'Data Availability Problem'. The mayor could be lying, and without the list, you have no way to prove it.
🤓 Expert Deep Dive
The 'Data Availability Problem' arises because it is impossible for a small mobile phone (Light Client) to download gigabytes of blockchain data to verify a block. To solve this, protocols use 'Data Availability Sampling' (DAS). Using 'Erasure Coding' (the same math used in CDs and QR codes), a block can be expanded such that only a small portion is needed to reconstruct the whole. A light node can download 1% of the block randomly; if those chunks are available, there is a 99.9% mathematical certainty that the ENTIRE block is available. This allows blockchains to scale significantly because verification no longer requires everyone to download everything. This concept is the heart of Ethereum's 'Danksharding' roadmap and modular DA layers like Celestia.