---
title: loading.js
description: API reference for the loading.js  file.
---

A **loading** file can create instant loading states built on [Suspense](/docs/app/building-your-application/routing/loading-ui-and-streaming).

By default, this file is a [Server Component](/docs/getting-started/react-essentials#server-components) - but can also be used as a Client Component through the `"use client"` directive.

```tsx filename="app/feed/loading.tsx" switcher
export default function Loading() {
  // Or a custom loading skeleton component
  return <p>'Loading...'</p>
}
```

```jsx filename="app/feed/loading.js" switcher
export default function Loading() {
  // Or a custom loading skeleton component
  return <p>'Loading...'</p>
}
```

Loading UI components do not accept any parameters.

> **Good to know**
>
> - While designing loading UI, you may find it helpful to use the [React Developer Tools](https://react.dev/learn/react-developer-tools) to manually toggle Suspense boundaries.

## Version History

| Version   | Changes               |
| --------- | --------------------- |
| `v13.0.0` | `loading` introduced. |
