A call like widget.querySelector("a") will thus only find a elements inside of the widget element, ignoring any other as that might be scattered throughout the document.

Pseudo-elements can also represent content that doesn’t exist in the source document at all, such as the ::before and ::after pseudo-elements which allow additional content to be inserted before or after the contents of any element.

The selector ::first-line is equivalent to *::first-line, which selects the ::first-line pseudo-element on every element in the document.

Does ::first-line:not(:focus) match anything?

Notice that ::first-line:hover is very different from :hover::first-line, which matches the first line of any originating element that is hovered! For example, :hover::first-line also matches the first line of a paragraph when the second line of the paragraph is hovered, whereas ::first-line:hover only matches if the first line itself is hovered.

  foo
  <"shadow root">
    
  

the selectors div > span and div::shadow ::slotted > span select the same element via different paths.

However, when rendered, the element generates boxes as if it were the child of the element, rather than the

3.7. Characters and case sensitivity

All Selectors syntax is ASCII case-insensitive (i.e. [a-z] and [A-Z] are equivalent), except for the parts that are not under the control of Selectors: specifically, the case-sensitivity of document language element names, attribute names, and attribute values depends on the document language.

Case sensitivity of namespace prefixes is defined in [CSS3NAMESPACE]. Case sensitivity of language ranges is defined in the :lang() section.

White space in Selectors consists of the code points SPACE (U+0020), TAB (U+0009), LINE FEED (U+000A), CARRIAGE RETURN (U+000D), and FORM FEED (U+000C). Other space-like code points, such as EM SPACE (U+2003) and IDEOGRAPHIC SPACE (U+3000), are never considered syntactic white space.

Code points in Selectors can be escaped with a backslash according to the same escaping rules as CSS. [CSS21] Note that escaping a code point “cancels out” any special meaning it may have in Selectors. For example, the selector #foo>a contains a combinator, but #foo\>a instead selects an element with the id foo>a.

3.8. Declaring Namespace Prefixes

Certain selectors support namespace prefixes. The mechanism by which namespace prefixes are declared should be specified by the language that uses Selectors. If the language does not specify a namespace prefix declaration mechanism, then no prefixes are declared. In CSS, namespace prefixes are declared with the @namespace rule. [CSS3NAMESPACE]

3.9. Invalid Selectors and Error Handling

User agents must observe the rules for handling invalid selectors:

• a parsing error in a selector, e.g. an unrecognized token or a token which is not allowed at the current parsing point (see overall § 18 Grammar and per-selector syntax definitions), causes that selector to be invalid.
• a simple selector containing an undeclared namespace prefix is invalid
• a selector containing an invalid simple selector, an invalid combinator or an invalid token is invalid.
• a selector list containing an invalid selector is invalid.
• an empty selector, i.e. one that contains no compound selector, is invalid.

Note: Consistent with CSS’s forwards-compatible parsing principle, UAs must treat as invalid any pseudo-classes, pseudo-elements, combinators, or other syntactic constructs for which they have no usable level of support. See Partial implementations.

An invalid selector represents, and therefore matches, nothing.

3.10. Legacy Aliases

Some selectors have a legacy selector alias. This is a name which, at parse time, is converted to the standard name (and thus does not appear anywhere in any object model representing the selector).

4. Logical Combinations

4.1. Selector Lists

A comma-separated list of selectors represents the union of all elements selected by each of the individual selectors in the selector list. (A comma is U+002C.) For example, in CSS when several selectors share the same declarations, they may be grouped into a comma-separated list. White space may appear before and/or after the comma.

h1 { font-family: sans-serif }
h2 { font-family: sans-serif }
h3 { font-family: sans-serif }

h1, h2, h3 { font-family: sans-serif }

Warning: the equivalence is true in this example because all the selectors are valid selectors. If just one of these selectors were invalid, the entire selector list would be invalid. This would invalidate the rule for all three heading elements, whereas in the former case only one of the three individual heading rules would be invalidated.

h1 { font-family: sans-serif }
h2..foo { font-family: sans-serif }
h3 { font-family: sans-serif }

h1, h2..foo, h3 { font-family: sans-serif } 

4.2. The Matches-Any Pseudo-class: :is()

The matches-any pseudo-class, :is(), is a functional pseudo-class taking a as its sole argument.

If the argument, after parsing, is an empty list, the pseudo-class is valid but matches nothing. Otherwise, the pseudo-class matches any element that matches any of the selectors in the list.

Note: The specificity of the :is() pseudo-class is replaced by the specificity of its most specific argument. Thus, a selector written with :is() does not necessarily have equivalent specificity to the equivalent selector written without :is() For example, if we have :is(ul, ol, .list) > [hidden] and ul > [hidden], ol > [hidden], .list > [hidden] a [hidden] child of an ol matches the first selector with a specificity of (0,2,0) whereas it matches the second selector with a specificity of (0,1,1). See § 17 Calculating a selector’s specificity.

Pseudo-elements cannot be represented by the matches-any pseudo-class; they are not valid within :is().

Default namespace declarations do not affect the compound selector representing the subject of any selector within a :is() pseudo-class, unless that compound selector contains an explicit universal selector or type selector.

*|*:is(:hover, :focus) 

*|*:is(*:hover, *:focus) 

As previous drafts of this specification used the name :matches() for this pseudo-class, UAs may additionally implement this obsolete name as a legacy selector alias for :is() if needed for backwards-compatibility.

4.3. The Negation (Matches-None) Pseudo-class: :not()

The negation pseudo-class, :not(), is a functional pseudo-class taking a selector list as an argument. It represents an element that is not represented by its argument.

Note: In Selectors Level 3, only a single simple selector was allowed as the argument to :not().

Note: The specificity of the :not() pseudo-class is replaced by the specificity of the most specific selector in its argument; thus it has the exact behavior of :not(:is(argument)). See § 17 Calculating a selector’s specificity.

Pseudo-elements cannot be represented by the negation pseudo-class; they are not valid within :not().

button:not([DISABLED]) 

*:not(FOO)

html|*:not(:link):not(:visited)

As with :is(), default namespace declarations do not affect the compound selector representing the subject of any selector within a :not() pseudo-class, unless that compound selector contains an explicit universal selector or type selector. (See :is() for examples.)

Note: The :not() pseudo-class allows useless selectors to be written. For instance :not(*|*), which represents no element at all, or div:not(span), which is equivalent to div but with a higher specificity.

4.4. The Specificity-adjustment Pseudo-class: :where()

The Specificity-adjustment pseudo-class, :where(), is a functional pseudo-class with the same syntax and functionality as :is(). Unlike :is(), neither the :where() pseudo-class, nor any of its arguments, contribute to the specificity of the selector—its specificity is always zero.

This is useful for introducing filters in a selector while keeping the associated style declarations easy to override.

a:not(:hover) {
  text-decoration: none;
}

nav a {
  /* Has no effect */
  text-decoration: underline;
}

a:where(:not(:hover)) {
  text-decoration: none;
}

nav a {
  /* Works now! */
  text-decoration: underline;
}

Note: Future levels of Selectors may introduce an additional argument to explicitly set the specificity of that instance of the pseudo-class.

4.5. The Relational Pseudo-class: :has()

The relational pseudo-class, :has(), is a functional pseudo-class taking a as an argument. It represents an element if any of the relative selectors would match at least one element when anchored against this element.

The :has() pseudo-class cannot be nested; :has() is not valid within :has(). Also, unless explicitly defined as a :has-allowed pseudo-element, pseudo-elements are not valid selectors within :has(). (This specification does not define any :has-allowed pseudo-elements, but other specifications may do so.)

Note: Pseudo-elements are generally excluded from :has() because many of them exist conditionally, based on the styling of their ancestors, so allowing these to be queried by :has() would introduce cycles.

For example, the following selector matches only elements that contain an child:

a:has(> img)

The following selector matches a

element immediately followed by another

element:

dt:has(+ dt)

The following selector matches

elements that don’t contain any heading elements:

section:not(:has(h1, h2, h3, h4, h5, h6))

Note that ordering matters in the above selector. Swapping the nesting of the two pseudo-classes, like:

section:has(:not(h1, h2, h3, h4, h5, h6))

...would result in matching any

element which contains anything that’s not a heading element.

5. Elemental selectors

5.1. Type (tag name) selector

A type selector is the name of a document language element type, and represents an instance of that element type in the document tree.

A type selector is written as a CSS qualified name: an identifier with an optional namespace prefix. [CSS3NAMESPACE] (See § 5.3 Namespaces in Elemental Selectors.)

5.2. Universal selector

The universal selector is a special type selector, that represents an element of any element type.

It is written as a CSS qualified name with an asterisk (* U+002A) as the local name. Like a type selector, the universal selector can be qualified by a namespace, restricting it to only elements belonging to that namespace, and is affected by a default namespace as defined in § 5.3 Namespaces in Elemental Selectors.

Unless an element is featureless, the presence of a universal selector has no effect on whether the element matches the selector. (Featureless elements do not match any selector, including the universal selector.)

The universal selector follows the same syntax rules as other type selectors: only one can appear per compound selector, and it must be the first simple selector in the compound selector.

Note: In some cases, adding a universal selector can make a selector easier to read, even though it has no effect on the matching behavior. For example, div :first-child and div:first-child are somewhat difficult to tell apart at a quick glance, but writing the former as div *:first-child makes the difference obvious.

5.3. Namespaces in Elemental Selectors

Type selectors and universal selectors allow an optional namespace component: a namespace prefix that has been previously declared may be prepended to the element name separated by the namespace separator “vertical bar” (| U+007C). (See, e.g., [XML-NAMES] for the use of namespaces in XML.) It has the following meaning in each form:

ns|E

elements with name E in namespace ns

*|E

elements with name E in any namespace, including those without a namespace

|E

elements with name E without a namespace

E

if no default namespace has been declared for selectors, this is equivalent to *|E. Otherwise it is equivalent to ns|E where ns is the default namespace.

@namespace foo url(http://www.example.com);
foo|h1 { color: blue }  /* first rule */
foo|* { color: yellow } /* second rule */
|h1 { color: red }      /* ...*/
*|h1 { color: green }
h1 { color: green }

If a default namespace is declared, compound selectors without type selectors in them still only match elements in that default namespace.

@namespace url("http://example.com/foo");

.special { ... }

A type selector or universal selector containing a namespace prefix that has not been previously declared is an invalid selector.

5.4. The Defined Pseudo-class: :defined

In some host languages, elements can have a distinction between being “defined”/“constructed” or not. The :defined pseudo-class matches elements that are fully defined, as dictated by the host language.

If the host language does not have this sort of distinction, all elements in it match :defined.

p:defined { ... }

custom-element { visibility: hidden }

custom-element:defined { visibility: visible }

6. Attribute selectors

Selectors allow the representation of an element’s attributes. When a selector is used as an expression to match against an element, an attribute selector must be considered to match an element if that element has an attribute that matches the attribute represented by the attribute selector.

Add comma-separated syntax for multiple-value matching? e.g. [rel ~= next, prev, up, first, last]

6.1. Attribute presence and value selectors

CSS2 introduced four attribute selectors:

[att]

Represents an element with the att attribute, whatever the value of the attribute.

[att=val]

Represents an element with the att attribute whose value is exactly "val".

[att~=val]

Represents an element with the att attribute whose value is a whitespace-separated list of words, one of which is exactly "val". If "val" contains whitespace, it will never represent anything (since the words are separated by spaces). Also if "val" is the empty string, it will never represent anything.

[att|=val]

Represents an element with the att attribute, its value either being exactly "val" or beginning with "val" immediately followed by "-" (U+002D). This is primarily intended to allow language subcode matches (e.g., the hreflang attribute on the a element in HTML) as described in BCP 47 ([BCP47]) or its successor. For lang (or xml:lang) language subcode matching, please see the :lang() pseudo-class.

Attribute values must be s or s. [CSS3SYN]

h1[title]

span[class="example"]

span[hello="Cleveland"][goodbye="Columbus"]

a[rel~="copyright"] { ... }
a[href="http://www.w3.org/"] { ... }

a[hreflang=fr] 

a[hreflang|="en"] 

DIALOGUE[character=romeo]
DIALOGUE[character=juliet]

6.2. Substring matching attribute selectors

Three additional attribute selectors are provided for matching substrings in the value of an attribute:

[att^=val]

Represents an element with the att attribute whose value begins with the prefix "val". If "val" is the empty string then the selector does not represent anything.

[att$=val]

Represents an element with the att attribute whose value ends with the suffix "val". If "val" is the empty string then the selector does not represent anything.

[att*=val]

Represents an element with the att attribute whose value contains at least one instance of the substring "val". If "val" is the empty string then the selector does not represent anything.

Attribute values must be s or s.

object[type^="image/"] 

a[href$=".html"] 

p[title*="hello"] 

6.3. Case-sensitivity

By default case-sensitivity of attribute names and values in selectors depends on the document language.

To match attribute values ASCII case-insensitively regardless of document language rules, the attribute selector may include the identifier i before the closing bracket (]). When this flag is present, UAs must match the attribute’s value ASCII case-insensitively (i.e. [a-z] and [A-Z] are considered equivalent).

Alternately, the attribute selector may include the identifier s before the closing bracket (]); in this case the UA must match the value case-sensitively, with “identical to” semantics [INFRA], regardless of document language rules.

Like the rest of Selectors syntax, the i and s identifiers themselves are ASCII case-insensitive.

[frame=hsides i] { border-style: solid none; } 

[type="a" s] { list-style: lower-alpha; }
[type="A" s] { list-style: upper-alpha; }

Note: Some document models normalize case-insensitive attribute values at parse time such that checking if a string is case-sensitive matching is impossible. Case-sensitive matching via s flags is only possible in systems that preserve the original case.

6.4. Attribute selectors and namespaces

The attribute name in an attribute selector is given as a CSS qualified name: a namespace prefix that has been previously declared may be prepended to the attribute name separated by the namespace separator "vertical bar" (|). In keeping with the Namespaces in the XML recommendation, default namespaces do not apply to attributes, therefore attribute selectors without a namespace component apply only to attributes that have no namespace (equivalent to |attr). An asterisk may be used for the namespace prefix indicating that the selector is to match all attribute names without regard to the attribute’s namespace.

An attribute selector with an attribute name containing a namespace prefix that has not been previously declared is an invalid selector.

@namespace foo "http://www.example.com";
[foo|att=val] { color: blue }
[*|att] { color: yellow }
[|att] { color: green }
[att] { color: green }

6.5. Default attribute values in DTDs

Attribute selectors represent attribute values in the document tree. How that document tree is constructed is outside the scope of Selectors. In some document formats default attribute values can be defined in a DTD or elsewhere, but these can only be selected by attribute selectors if they appear in the document tree. Selectors should be designed so that they work whether or not the default values are included in the document tree.

For example, a XML UA may, but is not required to, read an “external subset” of the DTD, but is required to look for default attribute values in the document’s “internal subset”. (See, e.g., [XML10] for definitions of these subsets.) Depending on the UA, a default attribute value defined in the external subset of the DTD might or might not appear in the document tree.

A UA that recognizes an XML namespace may, but is not required to use its knowledge of that namespace to treat default attribute values as if they were present in the document. (For example, an XHTML UA is not required to use its built-in knowledge of the XHTML DTD. See, e.g., [XML-NAMES] for details on namespaces in XML 1.0.)

Note: Typically, implementations choose to ignore external subsets. This corresponds to the behavior of non-validating processors as defined by the XML specification.

EXAMPLE[radix=decimal] { /*... default property settings ...*/ }
EXAMPLE[radix=octal]   { /*... other settings...*/ }

EXAMPLE                { /*... default property settings ...*/ }
EXAMPLE[radix=octal]   { /*... other settings...*/ }

6.6. Class selectors

The class selector is given as a full stop (. U+002E) immediately followed by an identifier. It represents an element belonging to the class identified by the identifier, as defined by the document language. For example, in [HTML5], [SVG11], and [MATHML] membership in a class is given by the class attribute: in these languages it is equivalent to the ~= notation applied to the local class attribute (i.e. [class~=identifier]).

*.pastoral { color: green }  /* all elements with class~=pastoral */ 

.pastoral { color: green }  /* all elements with class~=pastoral */ 

H1.pastoral { color: green }  /* H1 elements with class~=pastoral */ 

Not green
Very green

p.pastoral.marine { color: green } 

Note: Because CSS gives considerable power to the "class" attribute, authors could conceivably design their own "document language" based on elements with almost no associated presentation (such as div and span in HTML) and assigning style information through the "class" attribute. Authors should avoid this practice since the structural elements of a document language often have recognized and accepted meanings and author-defined classes may not.

Note: If an element has multiple class attributes, their values must be concatenated with spaces between the values before searching for the class. As of this time the working group is not aware of any manner in which this situation can be reached, however, so this behavior is explicitly non-normative in this specification.

When matching against a document which is in quirks mode, class names must be matched ASCII case-insensitively; class selectors are otherwise case-sensitive, only matching class names they are identical to. [INFRA]

6.7. ID selectors

Document languages may contain attributes that are declared to be of type ID. What makes attributes of type ID special is that no two such attributes can have the same value in a conformant document, regardless of the type of the elements that carry them; whatever the document language, an ID typed attribute can be used to uniquely identify its element. In HTML all ID attributes are named id; XML applications may name ID attributes differently, but the same restriction applies. Which attribute on an element is considered the “ID attribute“ is defined by the document language.

An ID selector consists of a “number sign” (U+0023, #) immediately followed by the ID value, which must be a CSS identifier. An ID selector represents an element instance that has an identifier that matches the identifier in the ID selector. (It is possible in non-conforming documents for multiple elements to match a single ID selector.)

h1#chapter1 

#chapter1 

*#z98y 

Note: In XML 1.0 [XML10], the information about which attribute contains an element’s IDs is contained in a DTD or a schema. When parsing XML, UAs do not always read the DTD, and thus may not know what the ID of an element is (though a UA may have namespace-specific knowledge that allows it to determine which attribute is the ID attribute for that namespace). If a style sheet author knows or suspects that a UA may not know what the ID of an element is, he should use normal attribute selectors instead: ''[name=p371] instead of #p371''.

If an element has multiple ID attributes, all of them must be treated as IDs for that element for the purposes of the ID selector. Such a situation could be reached using mixtures of xml:id, DOM3 Core, XML DTDs, and namespace-specific knowledge.

When matching against a document which is in quirks mode, IDs must be matched ASCII case-insensitively; ID selectors are otherwise case-sensitive, only matching IDs they are identical to. [INFRA]

7. Linguistic Pseudo-classes

7.1. The Directionality Pseudo-class: :dir()

The :dir() pseudo-class allows the author to write selectors that represent an element based on its directionality as determined by the document language. For example, [HTML5] defines how to determine the directionality of an element, based on a combination of the dir attribute, the surrounding text, and other factors. As another example, the its:dir and dirRule element of the Internationalization Tag Set [ITS20] are able to define the directionality of an element in [XML10].

The :dir() pseudo-class does not select based on stylistic states—for example, the CSS direction property does not affect whether it matches.

The pseudo-class :dir(ltr) represents an element that has a directionality of left-to-right (ltr). The pseudo-class :dir(rtl) represents an element that has a directionality of right-to-left (rtl). The argument to :dir() must be a single identifier, otherwise the selector is invalid. White space is optionally allowed between the identifier and the parentheses. Values other than ltr and rtl are not invalid, but do not match anything. (If a future markup spec defines other directionalities, then Selectors may be extended to allow corresponding values.)

The difference between :dir(C) and ''[dir=C]'' is that ''[dir=C]'' only performs a comparison against a given attribute on the element, while the :dir(C) pseudo-class uses the UAs knowledge of the document’s semantics to perform the comparison. For example, in HTML, the directionality of an element inherits so that a child without a dir attribute will have the same directionality as its closest ancestor with a valid dir attribute. As another example, in HTML, an element that matches ''[dir=auto]'' will match either :dir(ltr) or :dir(rtl) depending on the resolved directionality of the elements as determined by its contents. [HTML5]

7.2. The Language Pseudo-class: :lang()

If the document language specifies how the (human) content language of an element is determined, it is possible to write selectors that represent an element based on its content language. The :lang() pseudo-class, which accepts a comma-separated list of one or more language ranges, represents an element whose content language is one of the languages listed in its argument. Each language range in :lang() must be a valid CSS or . (Thus language ranges containing asterisks, for example, must be either correctly escaped or quoted as strings, e.g. :lang(\*-Latn) or :lang("*-Latn").)

Note: The content language of an element is defined by the document language. For example, in HTML [HTML5], the content language is determined by a combination of the lang attribute, information from meta elements, and possibly also the protocol (e.g. from HTTP headers). XML languages can use the xml:lang attribute to indicate language information for an element. [XML10]

An element’s content language matches a language range if, when represented in BCP 47 syntax [BCP47], it matches that language range in an extended filtering operation per [RFC4647] Matching of Language Tags (section 3.3.2). For this purpose, a wildcard language range ("*") does not match elements whose language is not tagged (e.g. lang=""), but does match elements whose language is tagged as undetermined (lang=und). The matching is performed ASCII case-insensitively. The language range does not need to be a valid language code to perform this comparison.

A language range consisting of an empty string (:lang("")) matches (only) elements whose language is not tagged.

Note: It is recommended that documents and protocols indicate language using codes from [BCP47] or its successor, and in the case of XML-based formats, by means of xml:lang attributes. [XML10] See “FAQ: Two-letter or three-letter language codes.”

html:lang(fr-be)
html:lang(de)
:lang(fr-be) > q
:lang(de) > q

Note: One difference between :lang(C) and the ''|='' operator is that the ''|='' operator only performs a comparison against a given attribute on the element, while the :lang(C) pseudo-class uses the UAs knowledge of the document’s semantics to perform the comparison.

  
Je suis français.

Note: Wildcard language matching and comma-separated lists are new in Level 4.

8. Location Pseudo-classes

8.1. The Hyperlink Pseudo-class: :any-link

The :any-link pseudo-class represents an element that acts as the source anchor of a hyperlink. For example, in [HTML5], any a or area elements with an href attribute are hyperlinks, and thus match :any-link. It matches an element if the element would match either :link or :visited, and is equivalent to :is(:link, :visited).

8.2. The Link History Pseudo-classes: :link and :visited

User agents commonly display unvisited hyperlinks differently from previously visited ones. Selectors provides the pseudo-classes :link and :visited to distinguish them:

• The :link pseudo-class applies to links that have not yet been visited.
• The :visited pseudo-class applies once the link has been visited by the user.

After some amount of time, user agents may choose to return a visited link to the (unvisited) :link state.

The two states are mutually exclusive.

.footnote:visited 

Since it is possible for style sheet authors to abuse the :link and :visited pseudo-classes to determine which sites a user has visited without the user’s consent, UAs may treat all links as unvisited links or implement other measures to preserve the user’s privacy while rendering visited and unvisited links differently.

8.3. The Local Link Pseudo-class: :local-link

The :local-link pseudo-class allows authors to style hyperlinks based on the users current location within a site. It represents an element that is the source anchor of a hyperlink whose target’s absolute URL matches the element’s own document URL. If the hyperlink’s target includes a fragment URL, then the fragment URL of the current URL must also match; if it does not, then the fragment URL portion of the current URL is not taken into account in the comparison.

nav :local-link { text-decoration: none; } 

Note: The current URL of a page can change as a result of user actions such as activating a link targeting a different fragment within the same page; or by use of the pushState API; as well as by the more obvious actions of navigating to a different page or following a redirect (which could be initiated by protocols such as HTTP, markup instructions such as , or scripting instructions ). UAs must ensure that :local-link, as well as the :target and :target-within pseudo-classes below, respond correctly to all such changes in state.

8.4. The Target Pseudo-class: :target

In some document languages, the document’s URL can further point to specific elements within the document via the URL’s fragment. The elements pointed to in this way are the target elements of the document.

The :target pseudo-class matches the document’s target elements. If the document’s URL has no fragment identifier, then the document has no target elements.

p.note:target 

:target { color : red }
:target::before { content : url(target.png) }

8.5. The Target Container Pseudo-class: :target-within

The :target-within pseudo-class applies to any element to which the :target pseudo class applies as well as to any element whose descendant in the flat tree (including non-element nodes, such as text nodes) matches the conditions for matching :target.

8.6. The Reference Element Pseudo-class: :scope

In some contexts, selectors are matched with respect to one or more scoping roots, such as when calling the querySelector() method in [DOM]. The :scope pseudo-class represents this scoping root, and may be either a true element or a virtual one (such as a DocumentFragment).

If there is no scoping root then :scope represents the root of the document (equivalent to :root). Specifications intending for this pseudo-class to match specific elements rather than the document’s root element must define their scoping root(s).

A virtual scoping root is some object representing the root of a document fragment, and can be used in selector patterns to represent other elements’ relationships to this scoping root, acting as the parent of any root elements in the document fragment it represents. A virtual scoping root is featureless and cannot be the subject of the selector.

9. User Action Pseudo-classes

Interactive user interfaces sometimes change the rendering in response to user actions. Selectors provides several user action pseudo-classes for the selection of an element the user is acting on. (In non-interactive user agents, these pseudo-classes are valid, but never match any element.)

These pseudo-classes are not mutually exclusive. An element can match several such pseudo-classes at the same time.

a:link    /* unvisited links */
a:visited /* visited links */
a:hover   /* user hovers */
a:active  /* active links */

a:focus
a:focus:hover

Note: The specifics of hit-testing, necessary to know when several of the pseudo-classes defined in this section apply, are not yet defined, but will be in the future.

9.1. The Pointer Hover Pseudo-class: :hover

The :hover pseudo-class applies while the user designates an element with a pointing device, but does not necessarily activate it. For example, a visual user agent could apply this pseudo-class when the cursor (mouse pointer) hovers over a box generated by the element. Interactive user agents that cannot detect hovering due to hardware limitations (e.g., a pen device that does not detect hovering) are still conforming; the selector will simply never match in such a UA.

An element also matches :hover if one of its descendants in the flat tree (including non-element nodes, such as text nodes) matches the above conditions.

Document languages may define additional ways in which an element can match :hover. For example, [HTML5] defines a labeled control element as matching :hover when its label is hovered.

Note: Since the :hover state can apply to an element because its child is designated by a pointing device, it is possible for :hover to apply to an element that is not underneath the pointing device.

The :hover pseudo-class can apply to any pseudo-element.

9.2. The Activation Pseudo-class: :active

The :active pseudo-class applies while an element is being activated by the user. For example, between the times the user presses the mouse button and releases it. On systems with more than one mouse button, :active applies only to the primary or primary activation button (typically the "left" mouse button), and any aliases thereof.

There may be document-language or implementation-specific limits on which elements can become :active. For example, [HTML5] defines a list of activatable elements.

An element also matches :active if one of its descendants in the flat tree (including non-element nodes, such as text nodes) matches the above conditions.

Document languages may define additional ways in which an element can match :active.

Note: An element can be both :visited and :active (or :link and :active).

9.3. The Input Focus Pseudo-class: :focus

The :focus pseudo-class applies while an element has the focus (accepts keyboard or mouse events, or other forms of input).

There may be document language or implementation specific limits on which elements can acquire :focus. For example, [HTML] defines a list of focusable areas.

Document languages may define additional ways in which an element can match :focus, except that the :focus pseudo class must not automatically propagate to the parent element—see :focus-within if matching on the parent is desired. (It may still apply to the parent element if made to propagate due to other mechanisms, but not merely due to being the parent.)

There’s a desire from authors to propagate :focus from a form control to its associated label element; the main objection seems to be implementation difficulty. See CSSWG issue (CSS) and WHATWG issue (HTML).

9.4. The Focus-Indicated Pseudo-class: :focus-visible

While the :focus pseudo-class always matches the currently-focused element, UAs only sometimes visibly indicate focus (such as by drawing a “focus ring”), instead using a variety of heuristics to visibly indicate the focus only when it would be most helpful to the user. The :focus-visible pseudo-class matches a focused element in these situations only, allowing authors to change the appearance of the focus indicator without changing when a focus indicator appears.

:root {
  --focus-gold: #ffbf47;
}

:focus-visible  {
  outline: 3px solid var(--focus-gold);
}

a:focus-visible {
  background-color: var(--focus-gold);
}

User agents should also use :focus-visible to specify the default focus style, so that authors using :focus-visible will not also need to disable the default :focus style.

9.5. The Focus Container Pseudo-class: :focus-within

The :focus-within pseudo-class applies to any element for which the :focus pseudo class applies as well as to an element whose descendant in the flat tree (including non-element nodes, such as text nodes) matches the conditions for matching :focus.

10. Time-dimensional Pseudo-classes

These pseudo-classes classify elements with respect to the currently-displayed or active position in some timeline, such as during speech rendering of a document, or during the display of a video using WebVTT to render subtitles.

CSS does not define this timeline; the host language must do so. If there is no timeline defined for an element, these pseudo-classes must not match the element.

Note: Ancestors of a :current element are also :current, but ancestors of a :past or :future element are not necessarily :past or :future as well. A given element matches at most one of :current, :past, or :future.

10.1. The Current-element Pseudo-class: :current

The :current pseudo-class represents the element, or an ancestor of the element, that is currently being displayed.

Its alternate form :current(), like :is(), takes a list of compound selectors as its argument: it represents the :current element that matches the argument or, if that does not match, the innermost ancestor of the :current element that does. (If neither the :current element nor its ancestors match the argument, then the selector does not represent anything.)

:current(p, li, dt, dd) {
  background: yellow;
}

10.2. The Past-element Pseudo-class: :past

The :past pseudo-class represents any element that is defined to occur entirely prior to a :current element. For example, the WebVTT spec defines the :past pseudo-class relative to the current playback position of a media element. If a time-based order of elements is not defined by the document language, then this represents any element that is a (possibly indirect) previous sibling of a :current element.

10.3. The Future-element Pseudo-class: :future

The :future pseudo-class represents any element that is defined to occur entirely after a :current element. For example, the WebVTT spec defines the :future pseudo-class relative to the current playback position of a media element. If a time-based order of elements is not defined by the document language, then this represents any element that is a (possibly indirect) next sibling of a :current element.

11. Resource State Pseudo-classes

The pseudo-classes in this section apply to elements that represent loaded resources, particularly images/videos, and allow authors to select them based on some quality of their state.

11.1. Media Playback State: the :playing, :paused, and :seeking pseudo-classes

The :playing pseudo-class represents an element that is capable of being “played” or “paused”, when that element is “playing”. (This includes both when the element is explicitly playing, and when it’s temporarily stopped for some reason not connected to user intent, but will automatically resume when that reason is resolved, such as a “buffering” or “stalled” state.)

The :paused pseudo-class represents an element that is capable of being “played” or “paused”, when that element is “paused” (i.e. not ”playing”). (This includes both an explicit “paused” state, and other non-playing states like “loaded, hasn’t been activated yet”, etc.)

The :seeking pseudo-class represents an element that is capable of ”seeking” when that element is ”seeking”. (For the audio and video elements of HTML, see HTML § 4.8.11.9 Seeking.)

11.2. Media Loading State: the :buffering and :stalled pseudo-classes

The :buffering pseudo-class represents an element that is capable of being “played” or “paused”, when that element cannot continue playing because it is actively attempting to obtain media data but has not yet obtained enough data to resume playback. (Note that the element is still considered to be “playing” when it is “buffering”. Whenever :buffering matches an element, :playing also matches the element.)

The :stalled pseudo-class represents an element when that element cannot continue playing because it is actively attempting to obtain media data but it has failed to receive any data for some amount of time. For the audio and video elements of HTML, this amount of time is the media element stall timeout. [HTML] (Note that, like with the :buffering pseudo-class, the element is still considered to be “playing” when it is “stalled”. Whenever :stalled matches an element, :playing also matches the element.)

11.3. Sound State: the :muted and :volume-locked pseudo-classes

The :muted pseudo-class represents an element capable of making sound when that element is “muted“ (forced silent). (For the audio and video elements of HTML, see muted. [HTML])

The :volume-locked pseudo-class represents an element capable of making sound when programmatically changing the element’s volume does not change the element’s effective media volume.

12. Element Display State Pseudo-classes

12.1. Collapse State: the :open and :closed pseudo-class

The :open pseudo-class represents an element that has both “open” and “closed” states, and which is currently in the “open” state.

The :closed pseudo-class represents an element that has both “open” and “closed” states, and which is currently in the closed state.

Exactly what “open” and “closed” mean is host-language specific, but exemplified by elements such as HTML’s details, select, and dialog elements, all of which can be toggled “open” to display more content (or any content at all, in the case of dialog).

Note: Being “open” or “closed” is a semantic state. An element not currently being displayed (for example, one that has visibility: collapse, or belongs to a display: none subtree) can still be “open” and will match :open.

12.2. Modal (Exclusive Interaction) State: the :modal pseudo-class

The :modal pseudo-class represents an element which is in a state that excludes all interaction with elements outside it until it has been dismissed. Multiple elements can be :modal simultaneously, with only one of them active (able to receive input).

12.3. Fullscreen Presentation State: the :fullscreen pseudo-class

The :fullscreen pseudo-class represents an element which is displayed in a mode that takes up most (usually all) of the screen, such as that defined by the Fullscreen API. [FULLSCREEN]

12.4. Picture-in-Picture Presentation State: the :picture-in-picture pseudo-class

The :picture-in-picture pseudo-class represents an element which is displayed in a mode that takes up most (usually all) of the viewport, and whose viewport is confined to part of the screen while being displayed over other content, for example when using the Picture-in-Picture API. [picture-in-picture]

13. The Input Pseudo-classes

The pseudo-classes in this section mostly apply to elements that take user input, such as HTML’s input element.

13.1. Input Control States

13.1.1. The :enabled and :disabled Pseudo-classes

The :enabled pseudo-class represents user interface elements that are in an enabled state; such elements must have a corresponding disabled state.

Conversely, the :disabled pseudo-class represents user interface elements that are in a disabled state; such elements must have a corresponding enabled state.

What constitutes an enabled state, a disabled state, and a user interface element is host-language-dependent. In a typical document most elements will be neither :enabled nor :disabled. For example, [HTML5] defines non-disabled interactive elements to be :enabled, and any such elements that are explicitly disabled to be :disabled.

Note: CSS properties that might affect a user’s ability to interact with a given user interface element do not affect whether it matches :enabled or :disabled; e.g., the display and visibility properties have no effect on the enabled/disabled state of an element.

13.1.2. The Mutability Pseudo-classes: :read-only and :read-write

An element matches :read-write if it is user-alterable, as defined by the document language. Otherwise, it is :read-only.

For example, in [HTML5] a non-disabled non-readonly element is :read-write, as is any element with the contenteditable attribute set to the true state.

13.1.3. The Placeholder-shown Pseudo-class: :placeholder-shown

Input elements can sometimes show placeholder text as a hint to the user on what to type in. See, for example, the placeholder attribute in [HTML5]. The :placeholder-shown pseudo-class matches an input element that is showing such placeholder text, whether that text is given by an attribute or a real element, or is otherwise implied by the UA.

13.1.4. The Automatic Input Pseudo-class: :autofill

The :autofill pseudo-class represents input elements that have been automatically filled by the user agent, and have not been subsequently altered by the user.

13.1.5. The Default-option Pseudo-class: :default

The :default pseudo-class applies to the one or more UI elements that are the default among a set of similar elements. Typically applies to context menu items, buttons and select lists/menus.

One example is the default submit button among a set of buttons. Another example is the default option from a popup menu. In a select-many group (such as for pizza toppings), multiple elements can match :default. For example, [HTML5] defines that :default matches the “default button” in a form, the initially-selected (s) in a , and a few other elements.

13.2. Input Value States

13.2.1. The Selected-option Pseudo-class: :checked

Radio and checkbox elements can be toggled by the user. Some menu items are “checked” when the user selects them. When such elements are toggled “on” the :checked pseudo-class applies. For example, [HTML5] defines that checked checkboxes, radio buttons, and selected elements match :checked.

While the :checked pseudo-class is dynamic in nature, and can altered by user action, since it can also be based on the presence of semantic attributes in the document (such as the selected and checked attributes in [HTML5]), it applies to all media.

An unchecked checkbox can be selected by using the negation pseudo-class:

input[type=checkbox]:not(:checked)

13.2.2. The Indeterminate-value Pseudo-class: :indeterminate

The :indeterminate pseudo-class applies to UI elements whose value is in an indeterminate state. For example, radio and checkbox elements can be toggled between checked and unchecked states, but are sometimes in an indeterminate state, neither checked nor unchecked. Similarly a progress meter can be in an indeterminate state when the percent completion is unknown. For example, [HTML5] defines how checkboxes can be made to match :indeterminate.

Like the :checked pseudo-class, :indeterminate applies to all media. Components of a radio-group initialized with no pre-selected choice, for example, would be :indeterminate even in a static display.

13.3. Input Value-checking

13.3.1. The Empty-Value Pseudo-class: :blank

The :blank pseudo-class applies to user-input elements whose input value is empty (consists of the empty string or otherwise null input).

Examples of :blank user-input elements would be a textarea element whose contents are empty, or an input field whose value is empty. Note that the value under consideration here is the value that would be submitted (see A form control’s value in [HTML]), which in HTML does not necessarily correspond to the value of the element’s value attribute.

Note: This selector is at-risk.

13.3.2. The Validity Pseudo-classes: :valid and :invalid

An element is :valid or :invalid when its contents or value is, respectively, valid or invalid with respect to data validity semantics defined by the document language (e.g. [XFORMS11] or [HTML5]). An element which lacks data validity semantics is neither :valid nor :invalid.

Note: There is a difference between an element which has no constraints, and thus would always be :valid, and one which has no data validity semantics at all, and thus is neither :valid nor :invalid. In HTML, for example, an

element may have no constraints, but a p element has no validity semantics at all, and so it never matches either of these pseudo-classes.

  
    Volume:
    
  
  ...

text

 
bla
this is not 
:empty

:nth-child(even)   /* represents the 2nd, 4th, 6th, etc elements
:nth-child(10n-1)  /* represents the 9th, 19th, 29th, etc elements */
:nth-child(10n+9)  /* Same */
:nth-child(10n+-1) /* Syntactically invalid, and would be ignored */

:nth-child(-n+3 of li.important)

li.important:nth-child(-n+3)

tr {
  background: white;
}
tr:nth-child(even) {
  background: silver;
}

tr {
  background: white;
}
tr:nth-child(even of :not([hidden])) {
  background: silver;
}

tr:nth-last-child(-n+2)    /* represents the two last rows of an HTML table */

foo:nth-last-child(odd)    /* represents all odd foo elements in their parent element,
                              counting from the last one */

div > p:first-child

 The last P before the note.

   
 The first P inside the note.

 The last P before the note.

   
 Note 
   
 The first P inside the note.

* > a:first-child /* a is first child of any element */
a:first-child /* Same (assuming a is not the root element) */

ol > li:last-child

img:nth-of-type(2n+1) { float: right; }
img:nth-of-type(2n) { float: left; }

body > h2:nth-of-type(n+2):nth-last-of-type(n+2) 

body > h2:not(:first-of-type):not(:last-of-type) 

dl dt:first-of-type

  
gigogne
  

    

      
fusée
      
multistage rocket
      
table
      
nest of tables
    
  

tr > td:last-of-type

h1 em

This headline
is very important

div * p

div p *[href]

body > p

div ol>li p

math + p

h1.opener + h2

h1 ~ pre

Definition of the function a
Function a(x) has to be applied to all figures in the table.
function a(x) = 12x/13.5

col.selected || td {
  background: gray;
  color: white;
  font-weight: bold;
}

  
  
  
A 
B 
C
  
D 
E
  
F 
G

*               /* a=0 b=0 c=0 */
LI              /* a=0 b=0 c=1 */
UL LI           /* a=0 b=0 c=2 */
UL OL+LI        /* a=0 b=0 c=3 */
H1 + *[REL=up]  /* a=0 b=1 c=1 */
UL OL LI.red    /* a=0 b=1 c=3 */
LI.red.level    /* a=0 b=2 c=1 */
#x34y           /* a=1 b=0 c=0 */
#s12:not(FOO)   /* a=1 b=0 c=1 */
.foo :is(.bar, #baz)
                /* a=1 b=1 c=0 */

 = 

 = #

 = #

 = #

 = #


 =  [ ?  ]*

 = ? 

 = [ ? *
                        [  * ]* ]!

 =  | 


 = '>' | '+' | '~' | [ '|' '|' ]

 =  | ? '*'

 = [  | '*' ]? '|'

 = ? 

 =  |  |
                       | 

 = 

 = '.' 

 = '['  ']' |
                       '['   [  |  ] ? ']'

 = [ '~' | '|' | '^' | '$' | '*' ]? '='

 = i | s

 = ':'  |
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 = ':'