attr()
Retrieves the value of an attribute from an element to use directly in CSS. The classic use is with the content property in pseudo-elements; using attr() with typed values on other properties is a newer experimental extension.
Quick example
a[data-tooltip]::before {
/* Displays the text from the data-tooltip attribute */
content: attr(data-tooltip);
position: absolute;
}attr() Browser Support
Limited availability99% global usage
This feature is not Baseline because it does not work in some of the most widely-used browsers.
Not ready for production without a fallback.