Glossary
Blob
A 128 KB chunk of data attached to an Ethereum transaction (EIP-4844), used by rollups for cheap data availability. Pruned by nodes after ~18 days.
Blobs were introduced by EIP-4844 as a dedicated cheap data lane for rollups. Each transaction can carry up to six 128-KB blobs, priced via their own fee market.
The data is not directly accessible to the EVM (contracts see only a KZG commitment), and nodes prune the blob bytes after a couple of weeks — long enough for rollup proofs to settle, but short enough not to inflate state storage forever. The result is order-of-magnitude cheaper data than calldata.