Crypto history
2024: Dencun gives rollups a separate data market
Blob transactions reduced one component of rollup costs without turning every layer 2 into the same security model.
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Why blobs were introduced
Dencun activated on Ethereum in March 2024 and included EIP-4844. Blob-carrying transactions provide a dedicated way to publish data used by rollups, with a fee mechanism separate from ordinary execution gas. Blob data is available for a limited period rather than being permanent application storage in the same form as contract state.
The distinction is economic and architectural. Rollups need data that allows their state to be reconstructed or checked. Before a dedicated data market, publishing that information could compete more directly with other execution-layer uses. The upgrade addressed that cost component.
A cheaper batch can still have dependencies
A low user fee does not disclose who operates a sequencer, who can upgrade the bridge or whether users have a practical exit during an outage. Nor does a proof of correct execution establish that data will be retrievable from every archive forever.
Optimistic rollups, validity proofs and data availability answer different parts of the design. Compare those properties alongside fees when reading post-Dencun adoption claims.