What was Ethereum's Dencun upgrade?

The Dencun upgrade was an Ethereum network upgrade that activated on March 13, 2024, and introduced proto-danksharding through EIP-4844. Its main goal was to cut the cost of posting layer 2 rollup data to Ethereum by adding a new kind of data called blobs. It was followed by the Pectra upgrade in 2025.

When was the Dencun upgrade date?

According to the Ethereum Foundation, Dencun activated at epoch 269568, around 13:55 UTC on March 13, 2024. Before that it ran on the Goerli, Sepolia and Holesky test networks in early 2024, as listed in the EIP-7569 meta document.

The name joins two upgrades that happened at once. Cancun was the execution layer upgrade, named after the city that hosted Devcon 3. Deneb was the consensus layer upgrade, named after a star, following Ethereum's convention of naming consensus upgrades after stars.

What is EIP-4844 proto-danksharding?

EIP-4844 added a new transaction type that carries blobs. A blob is a chunk of data, about 128 KB, that rides alongside a block but cannot be read by smart contracts. Rollups use blobs to publish their transaction batches instead of using permanent calldata, which had been their biggest cost.

Blobs are not kept forever. Ethereum nodes store them for about 18 days and then delete them. The ethereum.org FAQ explains that this window is longer than the typical seven-day rollup withdrawal period, which leaves room for anyone to check the data.

At launch, EIP-4844 targeted three blobs per block with a maximum of six. Blobs also got their own fee market, separate from normal gas, with a base fee that rises when demand stays above target. Our guide to Ethereum blobs explains blob fees in more detail. The "proto" in the name signals that this was a first step toward full danksharding, which would add far more data capacity later.

What else did Dencun change?

The Ethereum Foundation listed nine EIPs in Dencun. Beyond EIP-4844, they included:

• EIP-1153, transient storage that contracts can use within a single transaction.
• EIP-4788, which exposes the beacon chain block root inside the Ethereum Virtual Machine.
• EIP-5656, a new MCOPY instruction for copying memory.
• EIP-6780, which limits the SELFDESTRUCT opcode to contracts created in the same transaction.
• EIP-7516, a BLOBBASEFEE opcode.
• EIP-7044, EIP-7045 and EIP-7514, consensus changes covering validator exits, attestation timing and the validator churn limit.

What did the Dencun upgrade mean for users?

The Foundation told ETH holders they did not need to take any action unless their exchange or wallet said otherwise. Node operators and stakers had to update their software before the fork.

The practical effect was on layer 2 networks. Because blob space is cheaper than calldata, rollups that adopted blobs could lower their own costs, and the Foundation said it expected this to reduce layer 2 transaction fees. Actual fees still depend on demand for blob space and on each rollup's pricing.