Crypto glossary

Proto-Danksharding

Proto-danksharding, specified in EIP-4844, is an Ethereum upgrade that introduced blob transactions: a cheaper, temporary way for rollups to post their data to Ethereum, which lowered fees on layer 2 networks.

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The problem it solves

Rollups execute transactions off Ethereum's main chain and post compressed transaction data back to Ethereum, so anyone can verify or reconstruct their state. Before this upgrade, that data had to be stored as calldata, permanent and expensive space on Ethereum, which made data the largest part of most rollup fees.

How blobs work

EIP-4844 added a new transaction type that carries blobs, large chunks of data of about 128 kilobytes each. Blobs are attached to blocks but are not readable by smart contracts, and nodes only keep them for roughly 18 days before pruning them. That is long enough for anyone to download and check the data, but avoids storing it forever.

Blobs have their own fee market with a separate blob base fee that rises and falls with demand for blob space, independent of regular gas fees. The upgrade went live as part of the Dencun hard fork on 13 March 2024. Its name refers to researchers Protolambda and Dankrad Feist, and it is a first step toward full danksharding, a larger planned expansion of data capacity.

An example of the effect

Say a rollup used to pay most of its costs for posting data as calldata and passed that on to users. After moving that data into blobs, the same batch of transactions costs the rollup far less, so the fee for a simple swap on that layer 2 can drop substantially, while Ethereum still guarantees that the data was published.

Limits and trade-offs

Blob space is limited per block. When demand for blobs exceeds the target, the blob base fee rises quickly, so cheap rollup fees are not guaranteed forever. Because blobs are deleted after a few weeks, anyone who needs the historical data, such as block explorers or indexers, must store it themselves. And lower data costs on rollups do not change the trust assumptions of each rollup, such as who runs its sequencer.

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Frequently asked questions

Did proto-danksharding make Ethereum mainnet cheaper?

Not directly. It mainly reduced the cost for rollups to post data, which lowered fees on layer 2 networks.

What is the difference between proto-danksharding and full danksharding?

Proto-danksharding introduced the blob format and fee market. Full danksharding is a later plan to greatly expand blob capacity using techniques such as data availability sampling.

Are blobs stored forever?

No. Ethereum nodes prune blob data after roughly 18 days; a commitment to the data stays on-chain permanently.

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