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

The `fit` parameter controls how the image will be constrained within the provided size (`width` and `height`) values, in order to maintain the correct proportions.

## Syntax

```text
fit={value}
```

## Allowed values

| Value    | Description                                                                                           |
| -------- | ----------------------------------------------------------------------------------------------------- |
| `bounds` | Resize the image to fit entirely within the specified region, making one dimension smaller if needed. |
| `cover`  | Resize the image to entirely cover the specified region, making one dimension larger if needed.       |
| `crop`   | Resize and crop the image centrally to exactly fit the specified region.                              |

## Notes

The `fit` parameter has no effect unless both `width` and `height` are specified.

## Examples

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

| Example usage                                                                                         | Description                                                                    |
| ----------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------ |
| [`?width=150&height=150&fit=bounds`](https://www.fastly.io/image.jpg?width=150&height=150&fit=bounds) | Resize the image to fit within the bounds of 150px in width by 150px in height |
| [`?width=150&height=150&fit=cover`](https://www.fastly.io/image.jpg?width=150&height=150&fit=cover)   | Resize the image to entirely cover 150px in width by 150px in height           |
| [`?width=150&height=150&fit=crop`](https://www.fastly.io/image.jpg?width=150&height=150&fit=crop)     | Crop the image to 150px in width by 150px in height                            |