:id
Targets a single, unique element on a page that has a matching 'id' attribute. Since IDs must be unique, this selector should only ever match one element.
Quick example
#main-header {
/* Styles the unique element with id='main-header' */
background-color: #f3f4f6;
padding: 2rem;
}:id Browser Support
Widely available Since 2015 96% 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.
1+
1+
1+
12+