How do high-DPI devices like Retina displays and 1080p phones handle pixels in media queries?

问题

For example, how many pixels does the iPhone with a Retina display appear to a media query? Is it 320 pixels or 640 pixels? If it's 640 pixels, how can a website deal with different device resolutions? Is there any way to use units that are the same regardless of a screen's resolution?

回答1:

Retina devices like the iPhone and iPad usually use 2 device pixels = 1 CSS pixel. So a media query like this:

@media all and (max-width: 320px) {
}

actually will target an iPhone (portrait), even though it is 640 device pixels wide.

来源：https://stackoverflow.com/questions/23439307/how-do-high-dpi-devices-like-retina-displays-and-1080p-phones-handle-pixels-in-m