What are Ethereum blobs and how do blob fees work?

Ethereum blobs are large pieces of data that ride alongside Ethereum blocks, giving rollups a cheaper place to post their data than regular transaction space. They were introduced by EIP-4844, also called proto-danksharding, which went live in the Dencun upgrade on March 13, 2024. Ethereum.org says Dencun's main beneficiaries are layer 2 rollups and their users.

What is an Ethereum blob?

According to the EIP-4844 specification, each blob holds 4,096 pieces of 32 bytes, or 128 KiB of data. Ethereum's smart contracts cannot read what is inside a blob. They can only see a short cryptographic commitment to it, which lets anyone check that the data matches.

Blobs are also temporary. The spec requires nodes to serve blob data for 4,096 epochs, which works out to around 18 days, after which it can be deleted. That window gives anyone enough time to download the data and check a rollup's work, without every node storing it forever.

How do blob fees work?

Blobs use their own type of gas, separate from the gas used for normal transactions, so heavy demand on one side does not directly raise prices on the other. Each blob counts as 131,072 units of blob gas.

The blob base fee follows rules similar to Ethereum's regular base fee. When blocks carry more blobs than the target, the fee rises, and when they carry fewer, it falls. The spec says the blob fee is burned, and it is not refunded if a transaction fails. For how regular fees work, see our guide to gas fees.

Ethereum.org explains that blob fees could once fall to almost nothing, 1 wei, when demand was low. Fusaka added EIP-7918, which sets a reserve price under blob fees so rollups pay a meaningful amount for the space they use.

How much Ethereum blob space is there?

When EIP-4844 launched, the target was three blobs per block and the maximum was six. Ethereum.org notes that the Pectra upgrade raised the target to six.

The Fusaka upgrade, which went live on December 3, 2025, added PeerDAS (peer data availability sampling). Instead of every node downloading every blob, each full node stores about one eighth of the data, and missing pieces can be rebuilt from any half. This lets capacity grow without overloading node operators.

Fusaka also introduced blob parameter only forks, which raise blob limits without a full upgrade. The Ethereum Foundation scheduled the first on December 9, 2025, lifting the target from 6 to 10 and the maximum from 9 to 15, and the second on January 7, 2026, lifting them to 14 and 21. Later forks can raise these limits again, so the figures here reflect the schedule published before October 2026.