If you just use "em" scale for everything, you simply add another factor into the size calculation. It's the same as just using "px" directly, except it's now a

If you just use "em" scale for everything, you simply add another factor into the size calculation. It's the same as just using "px" directly, except it's now also larger/smaller depending on the font-scale, on top of the UI scale. Most of the time, on most devices, you won't notice that, but on some devices it will make everything unexpectedly larger or smaller, usually due to some vendor setting not matching well with devicePixelRatio. > You're commenting this underneath an article that explicitly complains that the pixel approach doesn't work today because OSes define fonts in points, because users can override your choices for font sizes, and because these units are not a uniform size across different operating systems. If you specify font size in "px" (instead of "pt"), font size will roughly match pixels/devicePixelRatio, which is as consistent as it gets across platforms. Using "em" instead would be less consistent. > Unless you're advocating that Gnome/iOS/Android/Mac should get rid of their current text scaling accessibility options, which... good luck. Pixels won't save you from that stuff, container widths based on current font size will, because for very good reasons you increasingly don't get the option on modern computers to force font to be a specific size. The intended behavior of changing the font size is to not scale the whole UI, just the fonts. If you use "em" for everything, you just defeat that feature. You might as well use "px" directly, it's more predictable and easier to think about.