<rem>
A CSS unit that is relative to the font-size of the root element (usually the <html> tag). Unlike 'em', it doesn't change based on the parent's font size, making scaling much more predictable.
Quick example
html {
font-size: 16px;
}
.my-text {
/* This will be exactly 32 pixels regardless of where it's nested */
font-size: 2rem;
}<rem> Browser Support
Widely availableSince 201586% global usage
This feature is well established and works across many devices and browser versions. It has been available across browsers since 2015.
Safe to use without fallbacks.
4+
3.6+
5+
12+