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GlossaryDDA (Data Availability)

DA (Data Availability)

DA is the mechanism ensuring rollup transaction data is accessible on Ethereum, preventing withholding attacks and enabling verification.

What is DA (Data Availability)?

In Ethereum rollups, data availability (DA) requires posting compressed transaction data—typically 16-32 KB per block—to the Layer 1 chain, which is Ethereum mainnet. This allows light clients to reconstruct states without trusting operators.

Post-Dencun upgrade in 2024, blobs provide 384 KB per block at 0.75 Ggas cost, reducing fees by 90% for rollups like Optimism. Rollups can opt for Ethereum’s external DA layer like Celestia, but Ethereum-native DA ensures censorship resistance.

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