> ## Documentation Index
> Fetch the complete documentation index at: https://docs.chainstack.com/llms.txt
> Use this file to discover all available pages before exploring further.

# eth_getUncleByBlockNumberAndIndex | Base

> Base API method that returns information about an uncle block by block number and uncle index position. Chainstack Base reference.

Base API method that returns information about an uncle block by block number and uncle index position. Note that uncles are a concept specific to proof-of-work chains and don't exist in proof-of-stake chains like Base.

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## Parameters

* `BLOCK PARAMETER` - the block number, or one of the following string values:
  * `"latest"` - the most recent block
  * `"earliest"` - the genesis block
  * `"pending"` - the pending block
  * `"safe"` - the most recent safe block
  * `"finalized"` - the most recent finalized block
* `UNCLE INDEX POSITION` - the uncle's index position. It's a hexadecimal value representing the uncle's position in the block's uncle list.

## Response

* `result` — A block object with uncle information, or null when no uncle exists at the given index. The block object includes:
  * `number`: The block number
  * `hash`: Hash of the uncle block
  * `parentHash`: Hash of the parent block
  * `nonce`: Hash of the generated proof-of-work
  * `sha3Uncles`: SHA3 of the uncles data in the block
  * `logsBloom`: The bloom filter for the logs of the block
  * `transactionsRoot`: The root of the transaction trie of the block
  * `stateRoot`: The root of the final state trie of the block
  * `receiptsRoot`: The root of the receipts trie of the block
  * `miner`: The address of the beneficiary to whom the mining rewards were given
  * `difficulty`: Integer of the difficulty for this block
  * `totalDifficulty`: Integer of the total difficulty of the chain until this block
  * `extraData`: The "extra data" field of this block
  * `size`: Integer the size of this block in bytes
  * `gasLimit`: The maximum gas allowed in this block
  * `gasUsed`: The total used gas by all transactions in this block
  * `timestamp`: The unix timestamp for when the block was collated

## Use case

The `eth_getUncleByBlockNumberAndIndex` method is primarily used in proof-of-work networks for:

* Historical analysis of uncle blocks at specific block heights
* Calculating mining rewards for uncle blocks
* Studying network fork behavior and block propagation
* Blockchain research and analysis tools

Note: In Base, which is a proof-of-stake chain, this method will typically return null as there are no uncle blocks in PoS networks.


## OpenAPI

````yaml /openapi/base_node_api/eth_getUncleByBlockNumberAndIndex.json POST /2fc1de7f08c0465f6a28e3c355e0cb14
openapi: 3.0.0
info:
  title: eth_getUncleByBlockNumberAndIndex example
  version: 1.0.0
  description: >-
    This is an API example for eth_getUncleByBlockNumberAndIndex, a method to
    retrieve information about an uncle block by block number and uncle index
    position.
servers:
  - url: https://base-mainnet.core.chainstack.com
security: []
paths:
  /2fc1de7f08c0465f6a28e3c355e0cb14:
    post:
      tags:
        - Ethereum Operations
      summary: eth_getUncleByBlockNumberAndIndex
      operationId: getUncleByBlockNumberAndIndex
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              properties:
                jsonrpc:
                  type: string
                  default: '2.0'
                method:
                  type: string
                  default: eth_getUncleByBlockNumberAndIndex
                id:
                  type: integer
                  default: 1
                params:
                  type: array
                  items:
                    type: string
                  minItems: 2
                  maxItems: 2
                  default:
                    - latest
                    - '0x0'
      responses:
        '200':
          description: Information about the uncle block
          content:
            application/json:
              schema:
                type: object
                properties:
                  jsonrpc:
                    type: string
                  id:
                    type: integer
                  result:
                    type: object
                    description: Uncle block object, or null when no uncle exists

````