Pseudo-classes

A CSS pseudo-class is a keyword added to selectors that specifies a special state of the element to be selected. For example :hover will apply a style when the user hovers over the element specified by the selector.

Pseudo-classes, together with pseudo-elements, let you apply a style to an element not only in relation to the content of the document tree, but also in relation to external factors like the history of the navigator (:visited, for example), the status of its content (like :checked on some form elements), or the position of the mouse (like :hover which lets you know if the mouse is over an element or not).

Syntax

selector:pseudo-class {
  property: value;
} 

Index of standard pseudo-classes

Specifications

Specification	Status	Comment
Fullscreen API	Living Standard	Defined :fullscreen.
WHATWG HTML Living Standard	Living Standard	No change from HTML5.
Selectors Level 4	Working Draft	Defined :any-link, :local-link, :scope, :active-drop-target, :valid-drop-target, :invalid-drop-target, :current, :past, :future, :placeholder-shown, :user-error, :blank, :nth-match(), :nth-last-match(), :nth-column(), :nth-last-column(), and :matches(). No significant change for pseudo-classes defined in Selectors Level 3 and HTML5 (though semantic meaning not taken over).
HTML5	Recommendation	Defined the semantic meaning, in the HTML context, of :link, :visited, :active, :enabled, :disabled, :checked, and :indeterminate. Defined :default, :valid, :invalid, :in-range, :out-of-range, :required, :optional, :read-only, :read-write, and :dir().
CSS Basic User Interface Module Level 3	Candidate Recommendation	Defined :default, :valid, :invalid, :in-range, :out-of-range, :required, :optional, :read-only, and :read-write, but without the associated semantic meaning.
Selectors Level 3	Recommendation	Defined :target, :root, :nth-child(), :nth-last-of-child(), :nth-of-type(), :nth-last-of-type(), :last-child, :first-of-type, :last-of-type, :only-child, :only-of-type, :empty, and :not(). Defined the syntax of :enabled, :disabled, :checked, and :indeterminate, but without the associated semantic meaning. No significant change for pseudo-classes defined in CSS Level 2 (Revision 1).
CSS Level 2 (Revision 1)	Recommendation	Defined :lang(), :first-child, :hover, and :focus. No significant change for pseudo-classes defined in CSS Level 1.
CSS Level 1	Recommendation	Defined :link, :visited, and :active, but without the associated semantic meaning.

See Also

• pseudo-elements