What Are Ethereum Blobs? EIP-4844 and Proto-Danksharding, Explained

Ethereum Improvement Proposal 4844, widely known as EIP-4844, introduced a new transaction format to the $ETH network that accepts "blobs" of data. These blobs provide a temporary, highly discounted storage space specifically designed to reduce the operating costs of Layer 2 networks. By isolating this data from the main execution layer, the upgrade created a distinct fee market that prevents rollup data needs from clogging the primary blockchain.

The Rollup Data Problem

To understand why blobs exist, one must look at how Ethereum scales. The base layer of Ethereum processes a limited number of transactions per second. To increase throughput, developers built Layer 2 rollups. These secondary networks process thousands of transactions off the main chain, bundle them into a single batch, and post the cryptographic proof and transaction data back to the Ethereum mainnet.

Historically, rollups posted this batch data using calldata, a designated space within a standard Ethereum transaction. Calldata is permanent. Every node operating on the Ethereum network must download and store it forever. Because storage space on a distributed network is finite and expensive, the Ethereum protocol charges high gas fees for calldata.

Before EIP-4844, rollups competed directly with standard users for block space. When decentralized finance activity spiked or high-profile NFT mints occurred, congestion drove up base layer fees. Rollups were forced to pay these exorbitant fees to post their calldata, passing the costs down to their own users. The network needed a way to provide data availability to rollups without forcing every node operator to store that data permanently.

Enter Proto-Danksharding

EIP-4844 implemented a concept called Proto-Danksharding. This is an intermediate step toward a future scaling architecture known as Full Danksharding. Proto-Danksharding introduces a new transaction type: the blob-carrying transaction.

A blob—short for Binary Large Object—is an opaque chunk of data attached to a transaction. Unlike calldata, blob data is not accessible to the Ethereum Virtual Machine (EVM), which is the computational engine that executes smart contracts. The EVM can see that the blob exists and can verify its cryptographic footprint, but it cannot read the actual contents of the blob.

By blinding the execution layer to the data, the network avoids the computational overhead of processing it. The primary purpose of a blob is simply to prove that the data was made available to the network for a certain period, satisfying the security requirements of Layer 2 rollups without burdening the base layer's execution environment.

The Mechanics of Blob-Carrying Transactions

When a rollup submits a batch of transactions using EIP-4844, it attaches the batch data as a blob. To ensure the data is mathematically verifiable without being read by the EVM, Ethereum uses a cryptographic tool called KZG commitments.

A KZG commitment acts as a small cryptographic fingerprint of the entire blob. The rollup smart contract on the mainnet checks this fingerprint to verify that the data published matches the proofs submitted by the Layer 2 network. If the rollup validators need to dispute a fraudulent transaction, they can reference the blob data using this commitment.

Because blobs do not compete for standard block space, they operate on a distinct fee market. Ethereum utilizes a multi-dimensional fee structure. Regular transactions bid for standard gas, while blob transactions bid for blob gas. This separation ensures that a sudden spike in regular mainnet activity does not necessarily increase the cost for rollups to post their data.

Consider a hypothetical numeric example to illustrate the fee separation. Assume the standard gas price on Ethereum is 50 gwei due to heavy decentralized exchange trading, making a standard transaction cost $5.00. Under the old calldata model, a rollup posting a 128-kilobyte data batch might consume 2 million gas, costing $100.00. With EIP-4844, that same 128-kilobyte batch is posted as a blob. Because the blob fee market is currently underutilized, the blob gas price sits at 1 gwei. The rollup pays just $2.00 to post the blob, completely bypassing the 50 gwei standard gas market. The cost savings are passed directly to Layer 2 users, making micro-transactions and complex contract interactions viable. This ties directly into broader network improvements, such as the push for Account Abstraction and Smart Wallets, which rely on cheap Layer 2 execution to function efficiently.

The 18-Day Pruning Window

The most distinct feature of blobs is their ephemeral nature. Storing megabytes of data per block indefinitely would rapidly bloat the Ethereum state, making it impossible for standard hardware to run a node. To solve this, EIP-4844 implements an automatic pruning mechanism.

Consensus nodes store blob data for approximately 18 days (precisely 4096 epochs). After this window, the blob data is deleted from the active node network. The 18-day period was selected carefully. Optimistic rollups require a seven-day challenge period during which network participants can flag fraudulent transactions. The 18-day window provides more than enough time for validators to download the data, check it for fraud, and finalize the rollup state.

Once the 18 days expire and the blobs are pruned, the data availability requirement is satisfied. Historical data preservation is shifted away from consensus nodes. Archival nodes, blockchain explorers, indexing protocols, and the rollups themselves are responsible for storing the long-term history of the network. The base layer Ethereum protocol only guarantees that the data was available long enough to secure the transition of the rollup's state.

Common Misconceptions

• Blobs make standard Ethereum transactions cheaper: EIP-4844 does not lower gas fees for users transacting directly on the Ethereum mainnet. It only lowers costs for Layer 2 networks utilizing blob-carrying transactions. Mainnet users still bid in the standard fee market.
• Smart contracts can read blob data: The EVM cannot access the contents of a blob. Smart contracts can only verify the cryptographic commitment attached to the blob. Data requiring direct mainnet execution must still use standard calldata.
• Blob data is permanently lost after 18 days: While consensus nodes delete blobs after the pruning window, the data is preserved by off-chain actors. Block explorers, dedicated data availability layers, and the rollups themselves maintain historical archives. The 18-day limit only applies to the mandatory storage requirements for node operators.

What to Watch

The introduction of blobs via EIP-4844 represents the foundation of Ethereum's rollup-centric roadmap. However, Proto-Danksharding is a transitional phase.

The next major milestone is Full Danksharding, which aims to increase the number of blobs attached to each block. To support massive data throughput without overloading node bandwidth, developers are researching Data Availability Sampling (DAS). DAS will allow nodes to verify that blob data is available by downloading only tiny, random fragments of the blob rather than the entire file.

Furthermore, the independent blob fee market remains subject to supply and demand dynamics. As more Layer 2 networks launch and transaction volumes grow, competition for blob space will increase. If the number of blobs per block hits the protocol's target capacity, blob gas prices will rise via an algorithmic adjustment similar to EIP-1559. Market participants must monitor blob utilization rates to gauge the long-term scalability of the rollup ecosystem.