[int_19h]

It was a historical distinction between the two OSes, even before Apple went all in on high-DPI.

Basically, macOS uses "ideal" font rendering, meaning that all glyph shapes and overall text size is as if they were rendered with infinite resolution and then quantized using the pixel grid; when you increase font size, the text scales linearly.

Windows, on the other hand, adjusts the shapes by snapping vertical and horizontal lines so that they correspond exactly to rows and columns of pixels. This distorts glyph shapes and spacing, but it makes small text (around 8-10pt) much more readable on low-DPI displays.

(Coincidentally, this seems to be why macOS default UI font has always been a bit larger and thicker than Windows.)

There are some screenshots to compare side by side here: https://damieng.com/blog/2007/06/13/font-rendering-philosoph...

[pathartl]

It's worth noting that article is from 2007 and is not fully representative of text rendering in modern Windows.

[int_19h]

While DirectWrite does render text a little bit differently, it still does pixel grid snapping (if you ask, which UI frameworks usually do) at least for small font sizes.

[lylejantzi3rd]

What's changed?