Fonts are often large files that take awhile to load. Some browsers hide text until the font loads, causing a flash of invisible text (FOIT).
How the font-display audit fails
Sitefig uses Lighthouse to test and flags any font URLs that may flash invisible text:
How to avoid showing invisible text
The easiest way to avoid showing invisible text while custom fonts load is to temporarily show a system font. By including font-display: swap in your @font-face style, you can avoid FOIT in most modern browsers:
@font-face {
font-family: 'Pacifico';
font-style: normal;
font-weight: 400;
src: local('Pacifico Regular'), local('Pacifico-Regular'), url(https://fonts.gstatic.com/s/pacifico/v12/FwZY7-Qmy14u9lezJ-6H6MmBp0u-.woff2) format('woff2');
font-display: swap;
}
The font-display API specifies how a font is displayed. swap tells the browser that text using the font should be displayed immediately using a system font. Once the custom font is ready, it replaces the system font. (See the Avoid invisible text during loading post for more information.)
Preload web fonts
Use <link rel="preload" as="font"> to fetch your font files earlier. Learn more:
- Preload web fonts to improve loading speed (codelab)
- Prevent layout shifting and flashes of invisibile text (FOIT) by preloading optional fonts
Google Fonts
Add the &display=swap parameter to the end of your Google Fonts URL:
<link href="https://fonts.googleapis.com/css?family=Roboto:400,700&display=swap" rel="stylesheet">Browser support
It's worth mentioning that not all major browsers support font-display: swap, so
you may need to do a bit more work to fix the invisible text problem.