# Source: https://docs.replit.com/extensions/development/react/hooks/useIsExtension.md

# useIsExtension() Hook

> The `useIsExtension()` hook returns whether the handshake has been successfully established with the Replit workspace. If the handshake is loading, `undefined` will be returned. After loading has finished, the hook will return a boolean.

## Usage

```ts  theme={null}
import { useIsExtension } from '@replit/extensions-react';

const Component = () => {
  const isExtension = useIsExtension();

  ...
}
```

## Signature

```ts  theme={null}
function useIsExtension(): boolean | undefined;
```