> ## Documentation Index
> Fetch the complete documentation index at: https://base-a060aa97-eb-mini-app-ia-overhaul.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# isEthereum

The `isEthereum` utility is designed to verify if the chain id is a valid Ethereum Mainnet or Ethereum Sepolia chain id.

## Usage

<CodeGroup>
  ```tsx code
  import { isEthereum } from '@coinbase/onchainkit';

  // Ethereum Mainnet (chain ID: 1)
  isEthereum({ chainId: 1 }); // returns true

  // Ethereum Sepolia (chain ID: 11155111)
  isEthereum({ chainId: 11155111 }); // returns true

  // Base (chain ID: 8453)
  isEthereum({ chainId: 8453 }); // returns false
  ```

  ```ts return value
  true; // When chainId is 1 (Ethereum Mainnet) or 11155111 (Ethereum Sepolia)
  false; // For all other chain IDs
  ```
</CodeGroup>

## Returns

`boolean` - Returns `true` if the chain id is Ethereum Mainnet or Ethereum Sepolia, otherwise `false`.

## Parameters

[`IsEthereumOptions`]: ./types#isethereumoptions