Since FF 59 Firefox is detecting wrong screen device-width and device-height for laptop Macbook retina screen at 1680x1050 px.

FF detects about half of the actual screen size.
Because of this it ends up using tablet CSS media query => @media screen and (min-device-width : 768px) and (max-device-width : 1024px).

Below are 3 screenshots from CSS3 MEDIA QUERIES TEST website, all made on same screen at 1680x1050 px with FF, Chrome and Safari.

FF detects wrong values while Chrome and Safari (latest versions) detect the correct values.

FF values for non retina (1 dppx) screens are correct.



Firefox 60.0.1 (WRONG values)



Chrome 66.0.3359.181 (CORRECT values)



Safari 11.1 (CORRECT values)