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Summary

This property returns the ratio of the resolution in physical pixels to the resolution in CSS pixels for the current display device. This value could also be interpreted as the ratio of pixel sizes: the size of one CSS pixel to the size of one physical pixel.

There are no callbacks or events to listen to when this value changes (for example, if you drag the window between displays with different densities).

Syntax

This property can be altered by overriding window.devicePixelRatio (for example, window.devicePixelRatio = 2)

value = window.devicePixelRatio;

Example

var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');

var canvasSize = 200;

//overriding default window.devicePixelRatio, changing it to 2 on retina display will make canvas clear
window.devicePixelRatio = 1;

canvas.width = canvas.height = canvasSize;

ctx.fillStyle = "#bada55";
ctx.fillRect(10, 10, 300, 300);
ctx.fillStyle = "#ffffff";
ctx.font = '18px Arial';
ctx.textAlign = 'center';
ctx.textBaseline = 'middle';

var x = canvasSize / 2;
var y = canvasSize / 2;

var textString = "I love MDN";
ctx.fillText(textString, x, y);

This image describe the impact of different value on retina display.

Specifications

Specification Status Comment
CSS Object Model (CSSOM) View Module
The definition of 'Window.devicePixelRatio' in that specification.
Working Draft Initial definition

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari
Basic support 49 (Yes) 49 11 41 9.1
Feature Android Edge Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support 4.4 (Yes) ? ? all 9.3

See also

Document Tags and Contributors

 Last updated by: kalpeshsingh,