Blob (EIP-4844)
A cheap, temporary data storage type introduced to Ethereum in March 2024, designed to make Layer 2 rollup data publication dramatically less expensive.
Blobs (Binary Large Objects) are a new transaction type introduced by EIP-4844 (Proto-Danksharding), activated on Ethereum in March 2024 as part of the Dencun upgrade. A blob is a fixed-size data packet (~128 KB) that can be attached to an Ethereum transaction at a fraction of the cost of equivalent calldata. Rollups use blobs to publish their transaction batch data to Ethereum's DA layer.
The key innovation is that blob data is not executed by the EVM and is automatically pruned by nodes after approximately 18 days — validators only need to guarantee availability for the challenge/proof window, not permanently. This allows Ethereum nodes to handle large amounts of rollup data without bloating the state indefinitely. EIP-4844 reduced L2 data costs by 5–10× immediately, with some L2s seeing 80–90% fee reductions overnight.
EIP-4844 is a stepping stone toward full Danksharding, which will increase the number of blobs per block dramatically (from 3–6 to potentially 64–128) and introduce Data Availability Sampling — allowing light nodes to verify data availability without downloading every blob. This is the endgame for scaling Ethereum's DA capacity to support thousands of rollups.