In this lesson
- find out what blobs are and why they made layer 2 networks cheaper
- understand what a fee on an L2 is made of
- learn why cheap L2s are linked to ETH's growing supply
A rollup used to send its data to Ethereum like an expensive registered letter, archived forever. Then Ethereum opened cheap container shipping: big boxes that get thrown away after a few weeks. Fees on layer 2 networks fell from dollars to fractions of a cent.
Blobs#
The Dencun upgrade (13 March 2024) added new space to blocks – blobs. They are big packets of data that:
- have their own fee market, separate from ordinary transactions,
- are deleted after about 18 days – long enough for anyone to download and check them,
- are not available to smart contracts; the network only guarantees that they existed.
Rollups moved their data into blobs and L2 fees fell by an order of magnitude.
Further growth#
| Upgrade | When | Blobs per block (target / maximum) |
|---|---|---|
| Dencun | 13 Mar 2024 | 3 / 6 |
| Pectra | 7 May 2025 | 6 / 9 |
| Fusaka + the BPO1 increase | Dec 2025 | 10 / 15 |
| the BPO2 increase | 7 Jan 2026 | 14 / 21 |
Fusaka also brought PeerDAS: nodes do not have to download whole blobs, it is enough to check random pieces. That way more blobs can be added without nodes needing a faster connection. In October 2026 demand for blobs is below the target, so their price stays near the minimum.
What you still pay for on an L2#
A fee on a rollup has three parts:
- computation on the L2 – gas similar to Ethereum's, only much cheaper,
- a share of the data – what the space in a blob on Ethereum costs, split between transactions,
- the operator's cut – what the rollup's operator keeps.
In a rush (a new token, an airdrop) the fee goes up on an L2 too – still more likely to cents than to dollars.
Cheap L2s, less burning#
Rollups pay very little for blobs, so almost nothing gets burned on Ethereum. That is why ETH's supply has grown again since 2024 (the lesson ETH as an asset). A win for users, a loss for the "ultrasound money" story – both are the result of the same decision.
A low fee does not mean low risk
Cheap transactions tempt you to be reckless: a hundred small trades, quick hops across bridges, buying unknown tokens. The fee is the least you can lose.
Common myths#
- "Blobs are stored forever." They are deleted after about 18 days; only the guarantee that they existed stays forever.
- "A fee on an L2 is always a fraction of a cent." In a rush it goes up there too.
- "Cheap L2s hurt Ethereum." They reduce the burn but bring users – whether that helps overall is an open question.
Summary
- Blobs (since Dencun in 2024) are cheap temporary space for rollup data.
- Pectra and Fusaka raised the number of blobs from 3 to 14 targeted per block.
- An L2 fee = computation + a share of a blob + the operator's cut.
- Cheap blobs mean little burning, which is why ETH's supply grows.