> ## Documentation Index
> Fetch the complete documentation index at: https://docs.theblockchainlibrary.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Blob

> A large temporary data object designed to carry rollup data more cheaply than permanent execution calldata.

# Blob

A large temporary data object designed to carry rollup data more cheaply than permanent execution calldata.

## Definition

A large temporary data object designed to carry rollup data more cheaply than permanent execution calldata.

## Why it matters

Scaling concepts explain how blockchain systems increase capacity while balancing security and decentralization.

## How it works

Blobs are carried in a specialized sidecar alongside a standard Ethereum block. They are not stored in the Ethereum Virtual Machine's state permanently, but are gossiped through the network nodes. After a short retention period, nodes delete the blob data, while the cryptographic commitment remains available on-chain for verification purposes.

## Real-world example

Optimism and Arbitrum use blobs to submit transaction batches to Ethereum, lowering user fees.

## Advantages

* Reduces L2 transaction costs
* Optimizes Ethereum storage efficiency
* Scales blockchain data throughput

## Limitations

* Data availability is time-limited
* Requires node storage synchronization

## Common misconceptions

* Users think blobs stay on the blockchain forever, but they are pruned for efficiency.
* Many believe blobs are general-purpose storage for dApps, but they are specifically for rollups.

## Related knowledge

* [Data Availability](/generated/v2/glossary/data-availability) — term
* [Layer 2](/categories/layer-2) — term
* [Rollup](/generated/v2/glossary/rollup) — term
* [Throughput](/generated/v2/glossary/throughput) — term

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**Canonical knowledge ID:** `glossary:blob`