rem
The rem CSS length unit is a font-relative length that is equal to the font size of the root HTML element which for most browsers is 16px.
Overview
The rem CSS length unit is a font-relative length that is equal to the font size of the root HTML element which for most browsers is 16px.
Browser support
| Feature | Desktop | Mobile | ||||
|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Safari | Chrome Android | Safari iOS | |
css.types.length.rem | 4 | 12 | 3.6 | 5 | 18 | 4 |
1+Supported (version) Not supported ※Has note Sub-feature descriptions sourced from MDN Web Docs (CC BY-SA 2.5)
Syntax
CSS
html {
font-size: 16px;
}
h1 {
font-size: 2rem; /* 32px */
}
.card {
padding: 1.5rem; /* 24px */
}Live demo
Use cases
Using rem
The rem CSS length unit is a font-relative length that is equal to the font size of the root HTML element which for most browsers is 16px.
Cautions
- May not be supported in older browsers.
Accessibility
- Make sure visual changes are conveyed appropriately to assistive technology.
Related links
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