Smart Clips are designed to simplify video editing workflows by automating the timing settings of your clips, 
removing the need to manually set the `start` and `length` properties. This is particularly useful when handling 
a large number of clips or when precise timing is difficult to determine in advance.

Smart clips provide you with options to automatically set `start` and `length` properties based on the assets
you are using.

### Automated timing

By setting the `start` or `length` of a clip to `auto`, Shotstack automatically calculates and assigns the
appropriate values based on the asset's duration and its position within the track.

This example will automatically set the `start` and `length` property:

```json
{
    "timeline": {
        "tracks": [
            {
                "clips": [
                   {
                       "asset":{
                           "type": "video",
                           "src": "https://s3-ap-southeast-2.amazonaws.com/my-bucket/footage.mp4",
                       },
                       "start": "auto",
                       "length": "auto"
                    }
                ]
            },
        ]
    }
}
```

For multiple clips, the `auto` setting stitches clips sequentially according to their order in the track,
maintaining their full length:

```json
{
    "timeline": {
        "tracks": [
            {
                "clips": [
                   {
                       "asset":{
                           "type": "video",
                           "src": "https://s3-ap-southeast-2.amazonaws.com/my-bucket/footage.mp4",
                       },
                       "start": "auto",
                       "length": "auto"
                    },
                    {
                       "asset":{
                           "type": "video",
                           "src": "https://s3-ap-southeast-2.amazonaws.com/my-bucket/footage2.mp4",
                       },
                       "start": "auto",
                       "length": "auto"
                    }
                ]
            },
        ]
    }
}
```

:::danger Warning

When using the `auto` setting for image, title or text assets (or luma assets used in conjunction with these assets),
the length will be automatically set to 3 seconds.

:::


### Persistent timing
To ensure a clip plays through to the end of your video timeline, set its length property to **end**. This 
configuration is useful for elements like watermarks or soundtracks that need to cover the entire video. If 
the clip's duration is shorter than the timeline's total duration, it will stop when the clip ends.

To add a watermark that appears throughout the entire duration of the video, you can configure the clip as 
follows:

```json
{
    "timeline": {
        "tracks": [
            {
                "clips": [
                    {
                        "asset": {
                            "type": "image",
                            "src": "https://shotstack-assets.s3.amazonaws.com/assets/logo.png"
                        },
                        "start": "auto",
                        "length": "end"
                    }
                ]
            },
            {
                "clips": [
                    {
                        "asset": {
                            "src": "https://s3-ap-southeast-2.amazonaws.com/my-bucket/footage.mp4",
                            "type": "video"
                        },
                        "start": "auto",
                        "length": "auto"
                    },
                    {
                        "asset": {
                            "src": "https://s3-ap-southeast-2.amazonaws.com/my-bucket/footage2.mp4",
                            "type": "video"
                        },
                        "start": "auto",
                        "length": "auto"
                    }
                ]
            }
        ]
    }
}
```