What is the best way to detect retina support on a device using JavaScript?

Question

Right now I am using this function:

function is_retina_device() {
    return window.devicePixelRatio > 1;
}

But its simplicity scares me

Answer 1

According to everything that I've read recently, browsers seem to be moving towards the resolution media query expression. This is instead of device-pixel-ratio that is being used in the currently accepted answer. The reason why device-pixel-ratio should only be used as a fallback is because it is not a standard media query.

According to w3.org:

Once upon a time, Webkit decided a media query for the screen resolution was needed. But rather than using the already-standardized resolution media query, they invented -webkit-device-pixel-ratio.

View Full Article

Resolution Media Query Documentation

Since resolution is standardized and therefore the future let's use that first in the detection for future proofing. Also because I'm not sure if you want to detect only high dppx devices or only retina(Apple only) devices, I've added one of each. Finally just as a note, the Apple detection is just user agent sniffing so can't be depended on. Note: for the isRetina function I'm using a dppx of 2 instead of 1.3 because all retina apple devices have a 2dppx.

Note it appears that MS Edge has some issues with non integer values

function isHighDensity(){
    return ((window.matchMedia && (window.matchMedia('only screen and (min-resolution: 124dpi), only screen and (min-resolution: 1.3dppx), only screen and (min-resolution: 48.8dpcm)').matches || window.matchMedia('only screen and (-webkit-min-device-pixel-ratio: 1.3), only screen and (-o-min-device-pixel-ratio: 2.6/2), only screen and (min--moz-device-pixel-ratio: 1.3), only screen and (min-device-pixel-ratio: 1.3)').matches)) || (window.devicePixelRatio && window.devicePixelRatio > 1.3));
}


function isRetina(){
    return ((window.matchMedia && (window.matchMedia('only screen and (min-resolution: 192dpi), only screen and (min-resolution: 2dppx), only screen and (min-resolution: 75.6dpcm)').matches || window.matchMedia('only screen and (-webkit-min-device-pixel-ratio: 2), only screen and (-o-min-device-pixel-ratio: 2/1), only screen and (min--moz-device-pixel-ratio: 2), only screen and (min-device-pixel-ratio: 2)').matches)) || (window.devicePixelRatio && window.devicePixelRatio >= 2)) && /(iPad|iPhone|iPod)/g.test(navigator.userAgent);
}