Ethereum Blobs: Temporary, Not Permanent
Ethereum blobs are temporary and not permanent as they are often misunderstood to be. According to Ethereum's current protocol, blob data has a minimum retention period of 4,096 epochs, approximately 18 days under normal network conditions.
This means that after the required retention period, Ethereum nodes can prune the blob contents, but the transaction containing the blob remains part of Ethereum's blockchain history. The blob's cryptographic commitment also remains available as part of the transaction-related blockchain data.
The temporary nature of blobs was introduced through EIP-4844 (Proto-Danksharding) to provide a cheaper way for Layer 2 rollups to make transaction data available without requiring every blob to become permanent blockchain history. This approach allows Ethereum to provide data availability without storing all that data permanently.