should use screen.width/window.innerWidth for chrome

[tsalufe]

because window.outerWidth ( and outerHeight) is not correct at page load or orientation change on android.On iOS, outerWidth seems to be 0.

[nigon1]

because window.outerWidth ( and outerHeight) is not correct at page load or orientation change on android.On iOS, outerWidth seems to be 0.

[qb20nh]

On non-maximized windows, you can detect browser zoom level(which is independent of system dpi) by resizing window and observing difference in ratio of change between innerWidth/innerHeight and outerWidth/innerHeight.