> ## Documentation Index
> Fetch the complete documentation index at: https://test-184b3b57.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# isBase

> Verify if a chain ID is a valid Base or Base Sepolia chain ID

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

### Parameters

<ParamField query="chainId" type="number" required>
  The chain ID to verify. For example, 8453 for Base Mainnet or 84532 for Base Sepolia.
</ParamField>

### Returns

<ResponseField name="boolean" type="boolean">
  Returns `true` if the chain ID is Base or Base Sepolia, otherwise `false`.
</ResponseField>

### Usage

```typescript theme={null}
import { isBase } from '@coinbase/onchainkit';
const chainId = 8453;
if (isBase({ chainId })) {
console.log('The chainId is Base.');
} else {
console.log('The chainId is not Base.');
}
```