CashboardGlossary · Onchain
What are blob fees?
Blob fees are what Ethereum rollups pay to post data in blobs, the short-lived data space EIP-4844 added, priced in a fee market separate from gas.
How do blob fees work?
Dencun went live on March 13, 2024 with EIP-4844, also called proto-danksharding. It gave Ethereum a second kind of block space: blobs, chunks of 131,072 bytes that ride along with a block but that the EVM cannot read. Rollups post their transaction batches there instead of in calldata. Consensus nodes keep blobs for about 18 days and then drop them.
Blobs have their own fee market, modeled on EIP-1559. Every blob uses 131,072 units of blob gas, and the blob base fee rises when blocks carry more blobs than the target and falls when they carry fewer. That fee is burned, like the normal base fee. The target has grown in steps: 3 blobs a block at Dencun, 6 after Pectra in May 2025, 10 in December 2025 and 14 since January 7, 2026, with a maximum of 21.
When demand stayed under the target, the old rule kept cutting the fee until it settled at 1 wei, and blob space was close to free. Fusaka, live since December 3, 2025, added EIP-7918. Once the blob base fee drops below a sixteenth of the regular base fee, it stops falling. Cheap mainnet gas still means cheap blobs, but not free ones.
Say the blob base fee is 0.02 gwei. One blob uses 131,072 blob gas, so it costs about 2,621 gwei, or 0.0000026 ETH. At a hypothetical ETH price of $3,000 that is under a cent for 128 KiB of rollup data, shared by every transaction in the batch.
Also called: blob gas, blob base fee, EIP-4844 blobs, blobspace.
Where do blob fees show up in Cashboard?
The Ethereum pulse shows the next block's blob base fee in gwei, or in wei once it drops under a thousandth of a gwei. Cost per blob prices one 128 KiB blob in dollars at the ultrasound.money ETH price. Blob space used says how full the last 20 blocks ran against the per-block maximum, with a tick on the bar at the protocol's blob target and a line giving the average blobs per block against it. When the fee sits near its floor of the base fee divided by 16, a note says so. Blob readings come from the same public RPC batch as gas, so when that fails, the gas and blob tiles both say the public RPC did not answer. The L2 scoreboard shows where the cost lands: each chain's median transaction cost, from growthepie data used under CC BY 4.0.
Frequently asked questions
Do blob fees change what I pay on an L2?
Yes, indirectly. The rollup pays blob fees to post its batches to Ethereum and passes the cost on through the L1 data part of each user fee. A blob carries many transactions, so each one pays a sliver. When blob space fills and the blob fee climbs, that sliver grows.
Why are blobs deleted after about 18 days?
Rollups only need the data long enough for honest parties to rebuild the rollup state and, on optimistic rollups, to prove fraud. Consensus nodes keep blobs for 4,096 epochs, about 18 days, and then drop them, so blob data does not pile up in Ethereum's history the way calldata does.
Where can you read more about blob fees?
Related terms
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