Understanding the :root Pseudo-Class in CSS
The :root pseudo-class in CSS represents the highest-level element in the document tree, which is usually the <html> element. While it often selects the same element as the html selector, there are important differences.
:rootis a pseudo-class that specifically targets the root element of the document, which is useful for defining global CSS variables (--variable-name).htmlis a type selector that selects all<html>elements. In standard HTML documents, there is only one, so it often overlaps with:root.:roothas higher specificity than thehtmlselector, so rules defined with:rootcan override those onhtmlif both are applied to the same properties.:rootis particularly useful in SVG documents or XML documents where the root element may not be<html>.
In this example, the :root pseudo-class is used to define a global CSS variable and set a font size. While the html selector could also set font size, :root is preferred for defining variables and ensures higher specificity.
Use
:rootfor defining CSS variables and global styles that may need to be referenced throughout the document.Use the
htmlselector for general styling of the HTML element when variables are not involved.Understand that
:roothas higher specificity thanhtml, so it can override html styles if necessary.Test styles in different document types (HTML, SVG) to ensure
:rootbehaves as expected.