Note that CSS pixels are not the same as physical pixels. Browsers are free to rescale CSS pixel values. Indeed, it's written in the document you linked to: >

Note that CSS pixels are not the same as physical pixels. Browsers are free to rescale CSS pixel values. Indeed, it's written in the document you linked to: > If the pixel density of the output device is very different from that of a typical computer display, the user agent should rescale pixel values. So actually 12px font should look about the same on all output devices, regardless of their physical DPI. But I agree that 12px is rather small for copy text.