The :is pseudo-class takes a list of selectors and selects any elements that matches the selectors in that list. Its useful to compact large selectors.
Take this example:
header h2,
nav h2,
article h2 {
color: black;
}
Can be written as:
is:(header, nav, article) h2 {
color: black;
}
It's worth noting there is a difference between :is
and :where()
when it comes to specificity value. Detailed explanations: