---
eip: 7516
title: BLOBBASEFEE instruction
description: Instruction that returns the current data-blob base-fee
author: Carl Beekhuizen (@carlbeek)
discussions-to: https://ethereum-magicians.org/t/eip-7516-blobbasefee-opcode/15761
status: Final
type: Standards Track
category: Core
created: 2023-09-11
requires: 3198, 4844
---

## Abstract

Add a `BLOBBASEFEE (0x4a)` instruction that returns the value of the blob base-fee of the current block it is executing in. It is the identical to [EIP-3198](./eip-3198.md) (`BASEFEE` opcode) except that it returns the blob base-fee as per [EIP-4844](./eip-4844.md).

## Motivation

The intended use case would be for contracts to get the value of the blob base-fee. This feature enables blob-data users to programmatically account for the blob gas price, eg:

- Allow rollup contracts to trustlessly account for blob data usage costs.
- Blob gas futures can be implemented based on it which allows for blob users to smooth out data blob costs.

## Specification

Add a `BLOBBASEFEE` instruction with opcode `0x4a`, with gas cost `2`.

| Op   | Input | Output | Cost |
|------|-------|--------|------|
| 0x4a | 0     | 1      | 2    |

`BLOBBASEFEE` returns the result of the `get_blob_gasprice(header) -> int` function as defined in [EIP-4844 §Gas accounting](./eip-4844.md#gas-accounting).

## Rationale

### Gas cost

The value of the blob base-fee is needed to process data-blob transactions. That means its value is already available before running the EVM code.
The instruction does not add extra complexity and additional read/write operations, hence the choice of `2` gas cost. This is also identical to [EIP-3198](./eip-3198.md) (`BASEFEE` opcode)'s cost as it just makes available data that is in the header.

## Backwards Compatibility

There are no known backward compatibility issues with this instruction.

## Test Cases

### Nominal Case

Assume calling `get_blob_gasprice(header)` (as defined in [EIP-4844 §Gas accounting](./eip-4844.md#gas-accounting)) on the current block's header returns `7 wei`:
`BLOBBASEFEE` should push the value `7` (left padded byte32) to the stack.

Bytecode: `0x4a00` (`BLOBBASEFEE, STOP`)

| Pc | Op          | Cost | Stack | RStack |
|----|-------------|------|-------|--------|
| 0  | BLOBBASEFEE | 2    | []    | []     |
| 1  | STOP        | 0    | [7]   | []     |

Output: 0x
Consumed gas: `2`

### Comprehensive Test Suite

A complete suite of tests can be found [here](https://github.com/ethereum/execution-spec-tests/blob/1983444bbe1a471886ef7c0e82253ffe2a4053e1/tests/cancun/eip7516_blobgasfee/test_blobgasfee_opcode.py).

## Security Considerations

The value of the blob base-fee is not sensitive and is publicly accessible in the block header. There are no known security implications with this instruction.

## Copyright

Copyright and related rights waived via [CC0](../LICENSE.md).