Is there a page somewhere that explains what it does? I’m not a particular fan of macOS font rendering though.

Then actually it might not help you too much... it's really a replacement font rendering engine for Windows (initially Windows GDI rendering and now they're adding in support for DirectWrite). It uses FreeType with various parameters to make the font rendering look more like macOS (in a nutshell: macOS doesn't use aggressive hinting to force the font shapes into the pixel grid, which makes it blurrier but more accurate on low-resolution screens; Windows does, and so it looks sharper on low-resolution screens).

However while looking around at a bug report to get MacType to work in Firefox [0] I came across a setting in Firefox's about:config [1] that can change the font rendering and that might help you out. Not sure about the history forking thing but there may be some Firefox extension to help with that.

[0] https://github.com/snowie2000/mactype/issues/673 [1] https://bugzilla.mozilla.org/show_bug.cgi?id=652141

Thanks. Yes, I tried all possible parameters for font rendering in Firefox. For some reason none of them match the sharpness of the IE rendering.

Have you considered using a 4K screen with 200% scaling? That would considerably sharpen text in any situation compared to a 1080p screen.

Yes, but (a) there’s too much software I still use that isn’t hi-DPI capable, and (b) I use a 1920x1200 display so would lose 10% vertical height, which is quite significant.

It’s all a question of trade-offs of course