---
title: contrast
summary: null
url: https://www.fastly.com/documentation/reference/io/contrast
---

The `contrast` parameter increases or decreases the difference between the darkest and lightest tones in an image.

## Syntax

```text
contrast={value}
```

`value` may be any number between -100 and 100.

## Notes

1. The default value is `0`. This leaves the image unchanged.
2. A value of `-100` will result in a fully grey image.

## Examples

Click the links to view the transformed image using a demo Fastly IO service.

| Example usage                                                 | Description             |
| ------------------------------------------------------------- | ----------------------- |
| [`?contrast=25`](https://www.fastly.io/image.jpg?contrast=25) | Increase contrast by 25 |