See https://en.wikipedia.org/wiki/Fallback_font https://en.wikipedia.org/wiki/Fallback_font. It typically isn’t a browser feature, but an OS one. Since 1998 Ma

See https://en.wikipedia.org/wiki/Fallback_font https://en.wikipedia.org/wiki/Fallback_font. It typically isn’t a browser feature, but an OS one. Since 1998 MacOS has a “last resort” font that has glyphs (not necessarily unique) for every Unicode code point. They donated it to Unicode (https://en.wikipedia.org/wiki/Fallback_font#Unicode_Last_Resort_font https://en.wikipedia.org/wiki/Fallback_font#Unicode_Last_Res...), so I expect most OSes running full-blown modern browsers to have it or something similar (those running smaller browser engines may be too space constrained to have room for it)