Why is my custom font not displaying correctly on Safari or iPhones?

Custom typography breaks on iOS and Safari when cross-origin resource sharing (CORS) rules block external web fonts, when font file formats lack legacy modern extensions (WOFF2), or when CSS @font-face rules are improperly cached.

“This one’s almost always a CORS restriction blocking the font file, or a missing modern font format Safari expects. I’ll get your typography rendering correctly within 24 hours for $99.”
— Jeff Bollettino, Managing Director, Ignite Conversions