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What was the Dencun upgrade?
Dencun was the Ethereum upgrade of March 13, 2024 that added blobs, a cheaper kind of data space for layer 2 rollups (EIP-4844, proto-danksharding). It joined Cancun, on the execution layer, and Deneb, on the consensus layer.
What it means for you
Fees on many layer 2 networks fell after Dencun, because rollups could post their data as blobs instead of the costlier calldata. Blob space has its own fee market, so layer 2 fees still rise when demand for blobs does.
How it works
A blob is data attached to a block that the consensus layer keeps for a limited period, long enough for anyone to check a rollup's data, and then drops; contracts cannot read it, only a commitment to it. That is what makes it cheaper than calldata, which every node keeps for good. Proto-danksharding is a first step toward full danksharding, which aims to raise the number of blobs much further. The Pectra upgrade of 2025 raised the target number of blobs per block.
Source: ethereum.org: The history of Ethereum (Dencun) · checked 5 October 2026
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