I always heard that in web design one should not prefer
pt as a size unit, because the browser/OS does not neccessarily know the correct
dpi. Result: final font sizes are not equal on different computers (Mac and Windows have different default
dpi, for example).
But isn't this true for the "prefered"
px as well? If I buy a FullHD monitor with 20" diameter and a FullHD monitor with 40" diameter, the font sizes will differ by a factor of two, because the physical pixel sizes are twice the size on the bigger monitor compared to the smaller one. So, for
px I have the same effect, because the browser does not know the device size.
Conclusion: If I take a ruler and measure a
pt based font on two different devices I can get different results (unknown real
dpi size). But for sure I can get different results for a
px based font size as well just because the same-resolution-device is bigger/smaller (unknown real physical pixel size).
So, why is the "unknown device parameter argument" used for
pt but not for
Bonus question: why do devices not deliver their physical size information via its device driver to the OS, anyways? A device should know how big it is and how much physical pixels it has, because someone build it with a defined size and pixel density and could just store this in the firmware.