fontfaceobserver VS unplugin-fonts

As for the flash of fallback fonts that occurs before the used google fonts are fully loaded (also known as FOUT or flash of unstyled text / type), one simple solution is to hide the root layout's content on init by wrapping everything in an element and hiding it or by displaying a "loading..." overlay. Then, all you have to do is detect when the webfonts are loaded, using something like FontFaceObserver, to reveal your app by updating the variable your wrapper's css class or the overlay element's display is bound to.

✗ https://github.com/bramstein/fontfaceobserver 456 KB

Another method, though involves more code but can work across all browsers involve the use of an external library called FontFaceObserver. To make this work, you have to;

Github

I wrote about loading a variable font that uses FontFaceObserver. This can be used to optimize your font loading.

I am not familiar with ePUB but you could use something like FontFaceObserver to do this pretty easily:

If you are using vue with vite, take a look at https://github.com/stafyniaksacha/vite-plugin-fonts