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Blob

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

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Definition

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

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Why it matters

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

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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.

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Real-world example

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

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Advantages

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

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Limitations

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

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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.
Canonical knowledge ID: glossary:blob