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


Device pixel ratio.

The `dpr` parameter provides a means to multiply image dimensions in order to translate logical pixels (also '[CSS pixels](https://developer.mozilla.org/en-US/docs/Glossary/CSS_pixel)') into physical pixels. The device pixel ratio is therefore the ratio between physical pixels and logical pixels.

It is usually possible for client-side software to query the host system to determine the DPR of the display the user is viewing. In web browsers, this is available as the [Window.devicePixelRatio](https://developer.mozilla.org/en-US/docs/Web/API/Window/devicePixelRatio) variable in JavaScript. The iPhone 5 reports a device pixel ratio of 2, because the physical linear resolution is double the logical resolution.

* Physical Resolution: 960 x 640
* Logical Resolution: 480 x 320

Other devices report varying device pixel ratios, including non-integer ones. For example, the Nokia Lumia 1020 reports `1.6667`, whereas the Samsung Galaxy S4 reports `3`.

## Syntax

```text
dpr={value}
```

`value` may be any number between 1 and 10.

## Examples

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

|Example usage|Description|
|-----------|-------------|
|[`?width=200&dpr=2`](https://www.fastly.io/image.jpg?width=200&dpr=2)|Resize the width to 400px (200 [CSS pixels](https://developer.mozilla.org/en-US/docs/Glossary/CSS_pixel) for screens with a device pixel ratio of 2)|