Generate automagical fluid typography, with new responsive properties for font-size, line-height, and letter-spacing. Built on PostCSS.

Inspired by this post.

Part of Rucksack - CSS Superpowers

• Usage
  • Quick start
  • Specify parameters
  • Expanded syntax
  • Responsive line-height and letter-spacing
  • Options
• Defaults
• Browser Support

html {
  font-size: responsive;
}

Pro tip: set a reaponsive font-size on html and use rem units throughout your project to make your whole UI fluid

Units can be in px, rem, or em. When using em units, be sure that the font-range is specified in em as well.

html {
  font-size: responsive 12px 21px; /* min-size, max-size */
  font-range: 420px 1280px; /* viewport widths between which font-size is fluid */
}

html {
  font-size: responsive;
  min-font-size: 12px;
  max-font-size: 21px;
  lower-font-range: 420px;
  upper-font-range: 1280px;
}

PostCSS Responsive Type also allows you to set fluid sizes for the line-height and letter-spacing properties. They have the same syntax and work the same way as responsive font sizes.

html {
  line-height: responsive 1.2em 1.8em;
  line-height-range: 420px 1280px;

  /* or extended syntax: */
  line-height: responsive;
  min-line-height: 1.2em;
  max-line-height: 1.8em;
  lower-line-height-range: 420px;
  upper-line-height-range: 1280px;
}

html {
  letter-spacing: responsive 0px 4px;
  letter-spacing-range: 420px 1280px;

  /* or extended syntax: */
  letter-spacing: responsive;
  min-letter-spacing: 0px;
  max-letter-spacing: 4px;
  lower-letter-spacing-range: 420px;
  upper-letter-spacing-range: 1280px;
}

Note: Unitless line heights are not supported.

{
    isRunOnExit: false,
}

• isRunOnExit (Boolean) - When true a postcss-responsive-type plugin will be called after all rest of postcss plugins. The default value is false.

To get started you only need to specify the responsive property, all other values have sane defaults.

• min-font-size: 14px

• max-font-size: 21px

• lower-font-range: 420px

• upper-font-range: 1280px

• min-line-height: 1.2em

• max-line-height: 1.8em

• lower-line-height-range: 420px

• upper-line-height-range: 1280px

• min-letter-spacing: 0px

• max-letter-spacing: 4px

• lower-letter-spacing-range: 420px

• upper-letter-spacing-range: 1280px

postcss-responsive-type just uses calc, vw units, and media queries behind the scenes, so it works on all modern browsers (IE9+). Although Opera Mini is not supported.

Legacy browsers will ignore the output responsive font-size. You can easily provide a simple static fallback:

.foo {
  font-size: 16px;
  font-size: responsive;
}

MIT © Sean King