The :has() CSS functional pseudo-class matches an element if any of the selectors passed as parameters would match at least one element.

The :dir() CSS functional pseudo-class matches elements by text direction, either right to left (rtl) or left to right (ltr).

The :user-valid and :user-invalid pseudo-classes match form controls that have been marked as valid or invalid based on their validation constraints.

The of syntax for the :nth-child() and :nth-last-child() CSS functional pseudo-classes match elements by the relative position of elements, counted from the first or last sibling matching a selector list.

The :modal pseudo-class selects elements that put other elements into a non-interactive state, such as a fullscreen element or a <dialog> element used with showModal().

The ::backdrop CSS pseudo-element is a box underneath an element in the top layer, such as a <dialog>. It can be used to create obscuring effects distinguishing a modal element from the elements underneath.

The :focus-visible CSS pseudo-class selects elements that match the :focus pseudo-class and meets the browser's criteria for visually emphasizing focused elements.

The ::file-selector-button CSS pseudo-element selects the button of a <input type="file"> element.

The :not() functional pseudo-class matches elements that do not match the selectors in its argument.

The :where() CSS functional pseudo-class takes a selector list as its argument, and matches any element that can be selected by one of the selectors in that list. It is functionally equivalent to the selectors in the list, but doesn't affect the CSS rule specificity.

The :is() CSS functional pseudo-class takes a selector list as its argument, and matches any element that can be selected by one of the selectors in that list.

The part and exportparts HTML attributes expose elements of a shadow DOM as named parts, which can be selected by the ::part() CSS pseudo-element for styling.

The i identifier in a CSS attribute selector matches attribute values case-insensitively in document languages like XML where attribute values are case-sensitive.

The :focus-within CSS pseudo-class matches an element if the element or any of its children are focused.

The :scope CSS pseudo-class matches the scoping root, for instance the element that querySelector() is called on, or the root of a DOM subtree specified with @scope.

The :link CSS pseudo-class matches unvisited links, :visited matches visited links, and :any-link matches both.

The :host CSS pseudo-class selects the containing element of the shadow tree in which it is used. The :host() CSS pseudo-class selects the that element only if it matches the provided selector.

The ::placeholder CSS pseudo-element selects help text in <input> and <textarea> elements when no value is set.

The :placeholder-shown CSS pseudo-element selects <input> and <textarea> elements when no value is set and the element's placeholder attribute is not empty. Not to be confused with ::placeholder, which selects the placeholder text itself.

The :default CSS pseudo-class matches the default element in a group of related form controls, such as checkboxes and radio buttons with the checked attribute.

CSS selectors match elements based on their type, attributes, and relationship to other elements. They define the specific elements to which a block of styles will be applied. This feature represents the oldest selectors of CSS.

The :empty CSS pseudo-class matches elements without child elements.

The :lang() CSS functional pseudo-class matches elements based on their content language.

The :root pseudo-class matches the root element of the document, usually the <html> element.

The :target CSS pseudo-class matches the element with an ID matching the URL fragment.

The :checked, :disabled, and :enabled CSS pseudo-classes match form elements based on their state.

The :active, :focus, and :hover CSS pseudo-classes match elements based on how users are interacting with them.

The :nth-of-type() and :nth-last-of-type() CSS functional pseudo-classes match elements based on their position among siblings of the same type. The :first-of-type, :last-of-type, and :only-of-type pseudo-classes match the first, last, and only elements of its type.

The form validity CSS pseudo-classes match <form> elements based on the constraints of a form field, such as validity (:valid, :invalid, :in-range, :out-of-range) and necessity (:optional or :required).

The @namespace CSS rule sets a default namespace or namespace prefix. Namespace prefixes allow CSS selectors to distinguish elements with the same name but different document types, such as the HTML <a> element and the SVG <a> element.