> ## Documentation Index
> Fetch the complete documentation index at: https://autorender.io/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Thumbnail

> Generate a WebP preview image from any video while preserving its aspect ratio.

`thumb_ar` extracts a frame from your video and returns it as a WebP image that keeps the source aspect ratio. Use it for previews, cards, and listing pages.

<Info>
  Thumbnails are returned as WebP, not video. The frame is rendered on the first request and served from cache thereafter.
</Info>

## How to use it?

Add `thumb_ar` as the only transform token in the path.

```text theme={null}
https://assets.autorender.io/LOKVTtKVGb/thumb_ar/doc/skateboarding.mp4
```

<img src="https://assets.autorender.io/LOKVTtKVGb/thumb_ar/doc/skateboarding.mp4" alt="Video thumbnail preview" style={{ maxWidth: '100%', display: 'block', marginLeft: 'auto', marginRight: 'auto', objectFit: 'contain' }} />

| Token      | What it does                                                         |
| ---------- | -------------------------------------------------------------------- |
| `thumb_ar` | Thumbnail that preserves the original aspect ratio, returned as WebP |

The first request triggers the render and returns a JSON status. Retry or poll the URL until it serves the WebP; see [async processing](/docs/video/introduction) for the status flow.

## Next steps

<CardGroup cols={2}>
  <Card title="Resize & aspect ratio" icon="crop-simple" iconType="solid" href="/docs/video/resize">
    Set exact dimensions or force a ratio for the source video.
  </Card>

  <Card title="Video overview" icon="clapperboard" iconType="solid" href="/docs/video/introduction">
    See every video transform token and how async rendering works.
  </Card>
</CardGroup>