RFS (abbreviation for responsive font size) is an algorithm which automatically calculates the appropriate font size based on the dimensions of the monitor or device. It's available in 5 languages:
- Font sizes will rescale for every screen or device, this prevents long words from being chopped off the screen on mobile devices.
- The minimum font size (configuration variable) will prevent the font size from becoming too small so readability can be assured.
- Super easy to use, no need to define complex configurations for each font size.
- Font sizes of all text elements will always remain in relation with each other.
RFS can be installed using a package manager (recommended):
npm:
$ npm install rfs --save
yarn:
$ yarn add rfs
Bower:
$ bower install rfs --save
Copy/paste (not recommended):
The source files can also be downloaded manually and used in a project. This method is not recommended because you lose the ability to easily and quickly manage and update RFS as a dependency.
.title {
@include responsive-font-size(4rem); // OR @include responsive-font-size(64px); OR @include rfs(64);
}.title
+responsive-font-size(4rem) // OR +responsive-font-size(64px) OR +rfs(64).title {
responsive-font-size: 4rem; // OR responsive-font-size: 64px; OR rfs: 64;
}.title {
.responsive-font-size(4rem); // OR .responsive-font-size(64px); OR .rfs(64);
} .title
responsive-font-size(4rem) // OR responsive-font-size(64px) OR rfs(64).title {
font-size: 4rem;
}
@media (max-width: 1200px) {
.title {
font-size: calc(1.6rem + 3.2vw);
}
}
SCSS, Sass & Stylus:
$rfs-minimum-font-size
Less:@rfs-minimum-font-size
PostCSS:minimumFontSize
The option will prevent the font size from becoming too small on smaller screens. If the font size which is passed to RFS is smaller than this minimum font size, no fluid font rescaling will take place.
Default value: 1rem
SCSS, Sass & Stylus:
$rfs-font-size-unit
Less:@rfs-font-size-unit
PostCSS:fontSizeUnit
The output font size will be rendered in this unit.
Default value: rem
SCSS, Sass & Stylus:
$rfs-breakpoint
Less:@rfs-breakpoint
PostCSS:breakpoint
Above this breakpoint, the font size will be equal to the font size you passed to RFS; below the breakpoint, the font size will dynamically scale.
Default value: 1200px
SCSS, Sass & Stylus:
$rfs-breakpoint-unit
Less:@rfs-breakpoint-unit
PostCSS:breakpointUnit
The width of the max width in the media query will be rendered in this unit.
Default value: px
SCSS, Sass & Stylus:
$rfs-factor
Less:@rfs-factor
PostCSS:factor
This value determines the strength of font size resizing. The higher the factor, the less difference there is between font sizes on small screens. The lower the factor, the less influence RFS has, which results in bigger font sizes for small screens. The factor must me greater than 1, setting it to 1 will disable dynamic rescaling.
Default value: 5
SCSS, Sass & Stylus:
$rfs-two-dimensional
Less:@rfs-two-dimensional
PostCSS:twoDimensional
Enabling the two dimensional media queries will determine the font size based on the smallest side of the screen with vmin. This prevents the font size from changing if the device toggles between portrait and landscape mode.
Default value: false
SCSS, Sass & Stylus:
$rfs-class
Less:@rfs-class
PostCSS:class
RFS can ben enabled or disabled with a class. There are 3 options:
disable
When the the disable classes are generated you can add the.disable-responsive-font-sizeclass to an element to disable responsive font sizes for the element and its child elements.enable
RFS is disabled by default in this case. The.enable-responsive-font-sizeclass can be added to an element to enable responsive font sizes for the element and its child elements.false
No extra classes are generated.
Default value: false
By setting a second parameter to true, !important is added after the font-size value. (Example is in scss)
.label {
@include responsive-font-size(2.5rem, true);
}CSS:
.label {
font-size: 2.5rem !important;
}
@media (max-width: 1200px) {
.label {
font-size: calc(1.3rem + 1.6vw) !important;
}
}Safari doesn't recalculate the value of vw in a calc()-function for font-sizes in iframes if the min-width, max-width or width is not set in vw after the iframe is resized (edge case, but this is the case for Codepen demo's). Adding this line will solve this (dirty fix):
_::-webkit-full-page-media, _:future, :root * {min-width: 0vw;}- Remember to set RFS on your font size of your
htmlorbody(especially if the minimum font size is lowered), otherwise some text may not dynamically rescale. Note that setting RFS onhtmlcan influence the value ofrem. - Always set your line-heights relative (in
emor unitless). - More tips and tricks with examples can be found here (written when only the SCSS version was made).
Martijn Cuppens
Code released under the MIT license.