Support Apple's dynamic text sizing in web content (iOS Safari & WebViews)

apple-web-dynamic-type.css

/*
  To support dynamic type in iOS, we need to set Apple's
  system font and then define font-families and rem-based
  font-sizes on descendant elements:
*/
@supports (font: -apple-system-body) {
  html {
    font: -apple-system-body;
  }
}

body {
  font-family: <your_font_family_here>;
}

p {
  font-size: 1.25rem;
}

/*
  If you've set a custom rem size in px on the html
  element, and want to maintain that on non-Apple
  devices, the font override muse be !important:
*/

body {
  font-size: 20px;
}

@supports (font: -apple-system-body) {
  html {
    font: -apple-system-body !important;
  }
}