> ## 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.

# isBase

The `isBase` utility is designed to verify if the chain id is a valid Base or Base Sepolia chain id.

## Usage

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

  // Base Mainnet (chain ID: 8453)
  isBase({ chainId: 8453 }); // returns true

  // Base Sepolia (chain ID: 84532)
  isBase({ chainId: 84532 }); // returns true

  // Ethereum (chain ID: 1)
  isBase({ chainId: 1 }); // returns false
  ```

  ```ts return value
  true; // When chainId is 8453 (Base Mainnet) or 84532 (Base Sepolia)
  false; // For all other chain IDs
  ```
</CodeGroup>

## Returns

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

## Parameters

[`IsBaseOptions`](./types#isbaseoptions) - See [`IsBaseOptions`](./types#isbaseoptions) for more details.