What is Blob? Blob's impact on the Ethereum network

After the Dencun update, the Ethereum network officially introduced EIP-4844, as well as a new concept in transaction types called "blob-carring transaction". Data blob has a positive impact on Ethereum and other Layer 2 networks.
The appearance of the “blob”
In the context of Rollups growing rapidly and strongly, practical updates are needed to help these projects expand further. Currently, Rollups are performing transactions by processing data off-chain, then collecting transactions into batches and sending them to Ethereum via the calldata feature.
Calldata: A feature in Ethereum transactions that allows the sender to add additional information attached to the transaction.
Costs related to call data are the largest costs Layer 2 projects must bear (accounting for more than 80% of total costs). This item alone caused the Rollup project to spend 15,000 ETH (about 34,000,000 USD) in February 2024.
Before moving to a roadmap focused on rollups, Ethereum had another ambitious roadmap focused on execution sharding, each execution shard could be designed with an environment that allows for the execution of different programs.
However, due to many different limitations and risks, Ethereum developers decided to turn to data sharding and solve the expansion problem for Rollups through “blobs”.
What is a blob and its characteristics?
Blob is a new data type specifically designed to provide temporary data storage space for Ethereum applications in general and Rollup in particular. The data blob format provides higher throughput at a cheaper cost than traditional calldata.
The special feature of data blobs is that they are processed, stored and verified by consensus nodes on the consensus layer, independent of execution nodes on the execution layer. This means EVM is inaccessible and does not store data in blobs, Rollup is the group that benefits the most from this upgrade.
To serve the purpose of short-term storage for blobs, Ethereum also had to create a new gas fee market, the data gas fee market, to price blob transactions separately from the old standard transactions.
Data storage space is sold in integer units of blobs, each blob is equivalent to 128 kB. The price for blob resource usage will be calculated according to the supply and demand situation of the market:

• The standard level is 3 blobs/block, equivalent to 384 kB. When the number of blobs used is greater than 3, the next blob price will increase by 12.5%, conversely, the blob price decreases by 12.5% ​​when the number of blobs used is less than or equal to 3.
• The maximum is 6 blobs/block, equivalent to 768 kB (0.75 MB).

With the above price, blob is expected to reduce data publishing fees by 65-90%, depending on the actual usage needs of the blob.
Meanwhile, regular transaction fees remain the same, with calldata charged at 16 gas/non-zero bytes and 4 gas/zero bytes. Only blob transactions use both gas fee markets.
This means the emergence of a dual fee market, allowing rollup to choose to publish transactions as calldata using a one-way fee mechanism (EIP-1559) or blob transactions using a two-way fee mechanism (EIP-1559 and EIP-4844).
The actual impact of blobs on the Ethereum network
Immediately after the Dencun upgraded version was successfully deployed, Layer 2 quickly deployed the update. zkSync, Starknet, Arbitrum, Base, Optimism are prominent projects that have released updated versions. Most of these projects recorded a significant decrease in transaction fees (sending ETH) due to a sharp decrease in data storage costs.
Starknet and zkSync were the first two projects to implement the upgrade, so at first the blob transactions on the network mainly came from these two ZK Rollup projects. After that, other projects also upgraded, the blob usage rate according to the current project is more balanced, Base and Arbitrum have risen to use the most blobs (each project accounts for about 30 - 35%). .
Some remaining Layer 2s such as Scroll, Linea, Polygon zkEVM have not been upgraded, transaction fees will still be higher than the above Layer 2s. Thanks to the Dencun update and the appearance of blobs, the Ethereum network is also relieved of its burden and ensures basic properties such as decentralization and security.
On the application layer side, projects that want to sponsor user gasless transactions through Paymaster will also benefit. In the last 6 months, these applications have spent a total of 1.8 million USD to sponsor gas fees, the average sponsorship fee per user is 0.14 USD.
After the EIP-4844 update, the project will only have to spend about 4,100 USD per month to fund daily transaction fees (NFT mint, familiarization transactions...) for 10,000 users. Before EIP-4844, the number would be up to 41,000 USD if you wanted to implement this strategy.
Summary
Blob transactions are one of the innovations successfully implemented by the Ethereum development team. This update not only benefits Ethereum itself, but also brings significant improvements to Rollups, reducing costs for users and application projects.
Layer 2 projects can use blob transactions more optimally in the future by aligning transaction execution times when the blob is full, coordinating with other L2 projects to share blob space, etc.
Some Layer 2s that have not upgraded blob transactions will suffer more or less losses compared to projects that have been successfully implemented.