Limited internationalization support. For example, trying to paste in مرحبًا (Arabic for "hello") just gives me tofu squares.
Used in in Android, Chrome, ChromeOS, Firefox, GNOME, GTK+, KDE, Qt, LibreOffice, OpenJDK, XeTeX, PlayStation, Microsoft Edge, Adobe Photoshop, Illustrator, InDesign, Godot Engine, Unreal Engine, ...