# Celestia Blobspace: Data Posted, Blob Fees and Rollups

> Celestia blobspace usage: data posted per day by rollup namespace, PayForBlobs fees in TIA, block square usage and the cost per megabyte beside Ethereum blobs.

Markdown copy of https://voltfincrypto.com/apps/celestia-blobspace

**Question:** How much data do rollups post to Celestia, what do they pay for it and how does the cost compare with Ethereum blobs?

- Kind: Dashboard in Voltfin Vantage
- Topic: [Layer 2s](https://voltfincrypto.com/topics/layer-2)
- Chains: Multi-chain, Ethereum
- Status: Planned. The data is not published yet, so this page states no figure; each figure will open its receipt when it is.

Celestia is a blockchain built to publish data for other chains. Rollups post their transaction batches to it as blobs, in PayForBlobs transactions paid in TIA, and each blob is tagged with a namespace so a rollup can find its own data. Light nodes check that the data is available by sampling small pieces of each block instead of downloading all of it.

This dashboard reads every PayForBlobs transaction to show how much data each rollup posts, what it pays and how full Celestia's blocks are against the limit in force. A second page sets the cost per megabyte on Celestia beside Ethereum's blob fees on the same days, since rollups choose between the two.

## Blueprint

### Usage

Data posted, fees paid and the rollups posting.

- **Data posted, latest day** (MB): Bytes posted in blobs on the latest complete day, in megabytes.
- **Blobs, latest day** (count): Blobs included in Celestia blocks on the latest complete day.
- **Fees paid, latest day** (TIA): TIA paid in PayForBlobs transactions on the latest complete day.
- **Cost per megabyte** (TIA): Fees paid divided by megabytes posted over the selected period.
- **Data posted by rollup by day** (MB): Megabytes posted each day, split by namespace and labelled by rollup where the label is known.
- **Rollups posting to Celestia**: Each namespace's rollup label, data posted, blobs, fees paid and share of all data over the period.

### Compared with Ethereum

Cost per megabyte on Celestia and on Ethereum blobs, with how full Celestia's blocks are.

- **Block space used** (%): The median share of the maximum data square that blocks filled over the selected period.
- **Celestia cost against Ethereum blobs** (× Ethereum): Celestia's cost per megabyte divided by Ethereum's blob cost per megabyte over the period, both in USD.
- **Cost per megabyte: Celestia and Ethereum** (USD): Daily cost per megabyte on Celestia and for Ethereum blobs, both in USD.

Filters: Rollup (Every rollup namespace posting to Celestia); Period (Last 7, 30 or 90 days).

## How it will be measured

- Blobs are read from MsgPayForBlobs transactions in each Celestia block: the namespace and size of each blob, the gas used and the fee paid in TIA.
- Rollups are identified by namespace from a reviewed registry, with the source of each label; namespaces without a label are shown as unlabelled rather than guessed.
- Cost per megabyte divides fees by bytes posted each day; the Ethereum comparison uses blob gas used and the blob base fee from Ethereum block headers on the same days, both converted to USD with prices recorded with their source.
- Block usage compares each block's data square with the largest square the chain's parameters allow at that height, so capacity upgrades show as a higher ceiling, not as a drop in demand.

## Data it needs

- `blob_usage_daily` (to build): EIP-4844 blobs posted per day, blob gas used, blob base fee, and the rollup that posted them.
- `native_prices_daily` (to build): Reference prices of major assets read from on-chain oracle feeds (Chainlink latestRoundData) at each day's last block, with each round's update time.
- Source: MsgPayForBlobs transactions in Celestia blocks: namespace, blob sizes, gas used and fee
- Source: Celestia block data square sizes and the maximum square size parameter at each height
- Source: Ethereum block headers: blob_gas_used and the blob base fee on the same days
- Source: A reviewed registry of rollup namespaces, recorded with the source of each label (off-chain)

## Questions

### What is Celestia blobspace?

The room in Celestia's blocks for blobs: chunks of data that rollups and other chains publish so anyone can check it is available. Celestia orders and publishes the data but does not execute it; each rollup reads its own namespace.

### How are Celestia blob fees calculated?

A PayForBlobs transaction uses gas in proportion to the bytes it posts, plus a fixed amount per transaction, and pays for that gas in TIA at a price the sender sets above the network minimum. The dashboard reports the fees actually paid, per day and per megabyte.

### What is a namespace on Celestia?

An identifier attached to every blob. Each rollup posts under its own namespace and downloads only that part of each block, with proofs that nothing in the namespace was left out.

### Is Celestia cheaper than Ethereum blobs?

It depends on demand on each side at the time. Both prices move with usage, so the comparison page measures the cost per megabyte on Celestia and on Ethereum day by day instead of assuming either is cheaper.

### What is data availability sampling?

A way for light nodes to check that a block's data was published without downloading all of it. The data is erasure-coded so that a block missing any part would fail random samples, and many small samples give high confidence.

## Glossary

- **Namespace**: The identifier on each Celestia blob that tells a rollup which data in a block is its own.
- **PayForBlobs**: The Celestia transaction type that posts one or more blobs and pays for them in TIA.
- **Data square**: The grid of shares a Celestia block's data is arranged in; its maximum size sets how much data a block can carry.

## Related apps

- [Ethereum Blob Fees and Blobs per Block vs Target](https://voltfincrypto.com/apps/ethereum-blob-fees)
- [EigenDA Tracker: Data Availability Usage, Operators and Stake](https://voltfincrypto.com/apps/eigenda-tracker)
- [L2 Profitability: Fees Earned vs Costs Paid to Ethereum](https://voltfincrypto.com/apps/l2-profitability)
- [Fusaka Upgrade Impact: Blobs, L2 Fees and Spam](https://voltfincrypto.com/apps/fusaka-upgrade-impact)
- [Ethereum Layer 2 List Ranked by Activity, Fees and Value](https://voltfincrypto.com/apps/ethereum-layer-2-list)
- [Ethereum TPS: Mainnet and Layer 2 Transactions per Second](https://voltfincrypto.com/apps/ethereum-tps)

Build it in Voltfin Studio: https://app.voltfincrypto.com/signup?next=%2F