---
eip: 3044
title: Adds `baseFee` to `eth_getBlockByNumber`
author: Abdelhamid Bakhta (@abdelhamidbakhta)
discussions-to: https://ethereum-magicians.org/t/eip-3044-add-basefee-to-eth-getblockbynumber/4828
status: Stagnant
type: Standards Track
category: Interface
created: 2020-10-14
requires: 1474, 1559
---

## Simple Summary
Add basefee field to `eth_getBlockByNumber` RPC endpoint response.

## Abstract
Adds `baseFee` property to the `eth_getBlockByNumber` JSON-RPC request `result` object.  This property will contain the value of the base fee for any block after the EIP-1559 fork.

## Motivation
[EIP-1559](./eip-1559.md) introduces a base fee per gas in protocol.
This value is maintained under consensus as a new field in the block header structure.
Users may need value of the base fee at a given block. Base fee value is important to make gas price predictions more accurate.

## Specification

### `eth_getBlockByNumber`

#### Description

Returns information about a block specified by number.
Every block returned by this endpoint whose block number is before the [EIP-1559](./eip-1559.md) fork block **MUST NOT** include a `baseFee` field.
Every block returned by this endpoint whose block number is on or after the [EIP-1559](./eip-1559.md) fork block **MUST** include a `baseFee` field.

#### Parameters

Parameters remain unchanged.

#### Returns
For the full specification of `eth_getBlockByNumber` see [EIP-1474](./eip-1474.md).
Add a new JSON field to the `result` object for block headers containing a base fee (post [EIP-1559](./eip-1559.md) fork block).

- {[`Quantity`](./eip-1474.md#quantity)} `baseFee` - base fee for this block

#### Example

```sh
# Request
curl -X POST --data '{
    "id": 1559,
    "jsonrpc": "2.0",
    "method": "eth_getBlockByNumber",
    "params":["latest", true]
}' <url>

# Response
{
    "id": 1559,
    "jsonrpc": "2.0",
    "result": {
        "difficulty": "0x027f07",
        "extraData": "0x0000000000000000000000000000000000000000000000000000000000000000",
        "baseFee": "0x7"
        "gasLimit": "0x9f759",
        "gasUsed": "0x9f759",
        "hash": "0xe670ec64341771606e55d6b4ca35a1a6b75ee3d5145a99d05921026d1527331",
        "logsBloom": "0xe670ec64341771606e55d6b4ca35a1a6b75ee3d5145a99d05921026d1527331",
        "miner": "0x4e65fda2159562a496f9f3522f89122a3088497a",
        "nonce": "0xe04d296d2460cfb8472af2c5fd05b5a214109c25688d3704aed5484f9a7792f2",
        "number": "0x1b4",
        "parentHash": "0x9646252be9520f6e71339a8df9c55e4d7619deeb018d2a3f2d21fc165dde5eb5",
        "sha3Uncles": "0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347",
        "size":  "0x027f07",
        "stateRoot": "0xd5855eb08b3387c0af375e9cdb6acfc05eb8f519e419b874b6ff2ffda7ed1dff",
        "timestamp": "0x54e34e8e"
        "totalDifficulty":  "0x027f07",
        "transactions": []
        "transactionsRoot": "0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421",
        "uncles": []
    }
}
```

## Rationale
The addition of a single parameter instead of introducing a whole new endpoint was the simplest change that would be easiest to get integrated.
For backward compatibility we decided to not include the base fee in the response for pre-1559 blocks.

## Backwards Compatibility
Backwards compatible. Calls related to block prior to [EIP-1559](./eip-1559.md) fork block will omit the base fee field in the response.

## Security Considerations
The added field (`baseFee`) is informational and does not introduce technical security issues.

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