What Is Dencun Upgrade?
Also known as: Dencun, Deneb-Cancun, Cancun-Deneb
In short
The Dencun upgrade is the Ethereum hard fork activated in March 2024 that introduced blob transactions through EIP-4844 (proto-danksharding), significantly lowering the data publishing costs of Layer 2 networks.
The name Dencun is a combination of two upgrades made at the same time: Deneb on the consensus layer and Cancun on the execution layer. In Ethereum, consensus layer upgrades are named after stars, while execution layer upgrades are named after the cities where Devcon conferences are held. Dencun is the major network upgrade after Shapella in 2023.
At the center of the upgrade is EIP-4844. Rollups previously wrote transaction data to Ethereum as permanent and expensive calldata. The blobs introduced with Dencun are temporary data spaces with a separate fee market that are deleted from nodes after a while. As a result, transaction fees on Layer 2 networks such as Arbitrum, Optimism and Base fell markedly after the upgrade.
The upgrade also includes other changes: EIP-1153 for transient storage, EIP-5656 for the MCOPY opcode that copies memory efficiently, EIP-4788, which gives the EVM access to consensus layer data, and EIP-6780, which restricts the function of the SELFDESTRUCT opcode. Dencun is seen as an intermediate step on the road to full danksharding.
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