If the OS cannot find Font X, it does not crash. Instead, it panics politely. It looks for a default "safety net" font—usually Arial, Times New Roman, or the system UI font. It then substitutes Font X with that default font. When DaFont says "Font substitution will occur," it means: The designer who uploaded this font did not include specific characters, or the internal naming structure of the font is broken. Consequently, if you try to use this font on a system that doesn't recognize it, your computer will replace it with a generic font.
When you download this font, your computer sees a file with no name. Windows has a rule: If a font has no name, you cannot select it in a dropdown menu. Because the OS cannot list the font, it immediately defaults to substitution the moment you try to type with it. Imagine you download a gorgeous display font that only contains uppercase letters (A-Z). You open Photoshop and start typing a sentence in lowercase: "Hello world." The font doesn't have a lowercase 'h,' 'e,' or 'l.' Font Substitution Will Occur Dafont
If you are a professional preparing files for a client or a printer, take the warning seriously. A font that triggers substitution on DaFont will almost certainly trigger substitution on a commercial printer’s RIP server, resulting in costly reprints. If the OS cannot find Font X, it does not crash
