Introduction#

CSS selectors identify specific HTML elements as targets for CSS styles. This topic covers how CSS selectors target HTML elements. Selectors use a wide range of over 50 selection methods offered by the CSS language, including elements, classes, IDs, pseudo-elements and pseudo-classes, and patterns.

Syntax#

• #id
• .classname
• :pseudo-classname
• ::pseudo-elementname
• [attr] /* has the attr attribute. */
• [attr=”value”] /* has the attr attribute, and its value is exactly ”value”. */
• [attr~=”value”] /* has the attr attribute, and its value, when split on whitespace, contains ”value”. */
• [attr|=”value”] /* has the attr attribute, and its value is exactly ”value“, or its value begins with ”value-”. */
• [attr^=”value”] /* has the attr attribute, and its value begins with ”value”. */
• [attr$=”value”] /* has the attr attribute, and its value ends with ”value”. */
• [attr*=”value”] /* has the attr attribute, and its value contains ”value”. */
• element-name
• *​

Remarks#

• Sometimes you will see double colons (::) instead of just one (:). This is a way to separate pseudo-classes from pseudo-elements.
• Old browsers, like Internet Explorer 8, only support a single colon (:) for defining pseudo-elements.
• Unlike pseudo-classes, only one pseudo-element may be used per selector, if present it must appear after the sequence of simple selectors that represents the subjects of the selector (a future version of the W3C specification may allow multiple pseudo-elements per selector).

Attribute Selectors

Overview

Attribute selectors can be used with various types of operators that change the selection criteria accordingly. They select an element using the presence of a given attribute or attribute value.

Notes:

1. The attribute value can be surrounded by either single-quotes or double-quotes. No quotes at all may also work, but it’s not valid according to the CSS standard, and is discouraged.

2. There is no single, integrated CSS4 specification, because it is split into separate modules. However, there are “level 4” modules. See browser support.

Details

[attribute]

Selects elements with the given attribute.

div[data-color] {
  color: red;
}

<div data-color="red">This will be red</div>
<div data-color="green">This will be red</div>
<div data-background="red">This will NOT be red</div>

Live Demo on JSBin

[attribute="value"]

Selects elements with the given attribute and value.

div[data-color="red"] {
  color: red;
}

<div data-color="red">This will be red</div>
<div data-color="green">This will NOT be red</div>
<div data-color="blue">This will NOT be red</div>

Live Demo on JSBin

[attribute*="value"]

Selects elements with the given attribute and value where the given attribute contains the given value anywhere (as a substring).

[class*="foo"] {
  color: red;
}

<div class="foo-123">This will be red</div>
<div class="foo123">This will be red</div>
<div class="bar123foo">This will be red</div>
<div class="barfooo123">This will be red</div>
<div class="barfo0">This will NOT be red</div>

Live Demo on JSBin

[attribute~="value"]

Selects elements with the given attribute and value where the given value appears in a whitespace-separated list.

[class~="color-red"] {
  color: red;
}

<div class="color-red foo-bar the-div">This will be red</div>
<div class="color-blue foo-bar the-div">This will NOT be red</div>

Live Demo on JSBin

[attribute^="value"]

Selects elements with the given attribute and value where the given attribute begins with the value.

[class^="foo-"] {
  color: red;
}

<div class="foo-123">This will be red</div>
<div class="foo-234">This will be red</div>
<div class="bar-123">This will NOT be red</div>

Live Demo on JSBin

[attribute$="value"]

Selects elements with the given attribute and value where the given attribute ends with the given value.

[class$="file"] {
  color: red;
}

<div class="foobar-file">This will be red</div>
<div class="foobar-file">This will be red</div>
<div class="foobar-input">This will NOT be red</div>

Live Demo on JSBin

[attribute|="value"]

Selects elements with a given attribute and value where the attribute’s value is exactly the given value or is exactly the given value followed by - (U+002D)

[lang|="EN"] {
  color: red;
}

<div lang="EN-us">This will be red</div>
<div lang="EN-gb">This will be red</div>
<div lang="PT-pt">This will NOT be red</div>

Live Demo on JSBin

[attribute="value" i]

Selects elements with a given attribute and value where the attribute’s value can be represented as Value, VALUE, vAlUe or any other case-insensitive possibility.

[lang="EN" i] {
  color: red;
}

<div lang="EN">This will be red</div>
<div lang="en">This will be red</div>
<div lang="PT">This will NOT be red</div>

Live Demo on JSBin

Specificity of attribute selectors

0-1-0

Same as class selector and pseudoclass.

*[type=checkbox] // 0-1-0

Note that this means an attribute selector can be used to select an element by its ID at a lower level of specificity than if it was selected with an ID selector: [id="my-ID"] targets the same element as #my-ID but with lower specificity.

See the Syntax Section for more details.

Combinators

Overview

Note: Sibling selectors target elements that come after them in the source document. CSS, by its nature (it cascades), cannot target previous or parent elements. However, using the flex order property, a previous sibling selector can be simulated on visual media.

Descendant Combinator: selector selector

A descendant combinator, represented by at least one space character ( ), selects elements that are a descendant of the defined element. This combinator selects all descendants of the element (from child elements on down).

div p {
  color:red;
}

<div>
  <p>My text is red</p>
  <section>
    <p>My text is red</p>
  </section>
</div>

<p>My text is not red</p>

Live Demo on JSBin

In the above example, the first two <p> elements are selected since they are both descendants of the <div>.

Child Combinator: selector > selector

The child (>) combinator is used to select elements that are children, or direct descendants, of the specified element.

div > p {
  color:red;
}

<div>
  <p>My text is red</p>
  <section>
    <p>My text is not red</p>
  </section>
</div>

Live Demo on JSBin

The above CSS selects only the first <p> element, as it is the only paragraph directly descended from a <div>.

The second <p> element is not selected because it is not a direct child of the <div>.

Adjacent Sibling Combinator: selector + selector

The adjacent sibling (+) combinator selects a sibling element that immediate follows a specified element.

p + p {
  color:red;
}

<p>My text is not red</p>
<p>My text is red</p>
<p>My text is red</p>
<hr>
<p>My text is not red</p>

Live Demo on JSBin

The above example selects only those <p> elements which are directly preceded by another <p> element.

General Sibling Combinator: selector ~ selector

The general sibling (~) combinator selects all siblings that follow the specified element.

p ~ p {
  color:red;
}

<p>My text is not red</p>
<p>My text is red</p>
<hr>
<h1>And now a title</h1>
<p>My text is red</p>

Live Demo on JSBin

The above example selects all <p> elements that are preceded by another <p> element, whether or not they are immediately adjacent.

Class Name Selectors

The class name selector select all elements with the targeted class name. For example, the class name .warning would select the following <div> element:

<div class="warning">
    <p>This would be some warning copy.</p>
</div>

You can also combine class names to target elements more specifically. Let’s build on the example above to showcase a more complicated class selection.

CSS

.important {
    color: orange;
}
.warning {
    color: blue;
}
.warning.important {
    color: red;
}

HTML

<div class="warning">
    <p>This would be some warning copy.</p>
</div>

<div class="important warning">
    <p class="important">This is some really important warning copy.</p>
</div>

In this example, all elements with the .warning class will have a blue text color, elements with the .important class with have an orange text color, and all elements that have both the .important and .warning class name will have a red text color.

Notice that within the CSS, the .warning.important declaration did not have any spaces between the two class names. This means it will only find elements which contain both class names warning and important in their class attribute. Those class names could be in any order on the element.

If a space was included between the two classes in the CSS declaration, it would only select elements that have parent elements with a .warning class names and child elements with .important class names.

ID selectors

ID selectors select DOM elements with the targeted ID. To select an element by a specific ID in CSS, the # prefix is used.

For example, the following HTML div element…

<div id="exampleID">
    <p>Example</p>
</div>

…can be selected by #exampleID in CSS as shown below:

#exampleID {
    width: 20px;
}

Note: The HTML specs do not allow multiple elements with the same ID

Pseudo-classes

Pseudo-classes are keywords which allow selection based on information that lies outside of the document tree or that cannot be expressed by other selectors or combinators. This information can be associated to a certain state (state and dynamic pseudo-classes), to locations (structural and target pseudo-classes), to negations of the former (negation pseudo-class) or to languages (lang pseudo-class). Examples include whether or not a link has been followed (:visited), the mouse is over an element (:hover), a checkbox is checked (:checked), etc.

Syntax

selector:pseudo-class { 
    property: value;
}

List of pseudo-classes:

The :visited pseudoclass can’t be used for most styling in a lot of modern browsers anymore because it’s a security hole. See this link for reference.

Basic selectors

Note: The value of an ID must be unique in a web page. It is a violation of the HTML standard to use the value of an ID more than once in the same document tree.

A complete list of selectors can be found in the CSS Selectors Level 3 specification.

How to style a Range input

HTML

<input type="range"></input>

CSS

Global boolean with checkbox:checked and ~ (general sibling combinator)

With the ~ selector, you can easily implement a global accessible boolean without using JavaScript.

Add boolean as a checkbox

To the very beginning of your document, add as much booleans as you want with a unique id and the hidden attribute set:

<input type="checkbox" id="sidebarShown" hidden />
<input type="checkbox" id="darkThemeUsed" hidden />

<!-- here begins actual content, for example: -->
<div id="container">
    <div id="sidebar">
        <!-- Menu, Search, ... -->
    </div>

    <!-- Some more content ... -->
</div>

<div id="footer">
    <!-- ... -->
</div>

Change the boolean’s value

You can toggle the boolean by adding a label with the for attribute set:

<label for="sidebarShown">Show/Hide the sidebar!</label>

Accessing boolean value with CSS

The normal selector (like .color-red) specifies the default properties. They can be overridden by following true / false selectors:

/* true: */
<checkbox>:checked ~ [sibling of checkbox & parent of target] <target>

/* false: */
<checkbox>:not(:checked) ~ [sibling of checkbox & parent of target] <target>

Note that <checkbox>, [sibling ...] and <target> should be replaced by the proper selectors. [sibling ...] can be a specific selector, (often if you’re lazy) simply * or nothing if the target is already a sibling of the checkbox.

Examples for the above HTML structure would be:

#sidebarShown:checked ~ #container #sidebar {
    margin-left: 300px;
}

#darkThemeUsed:checked ~ #container,
#darkThemeUsed:checked ~ #footer {
    background: #333;
}

In action

See this fiddle for a implementation of these global booleans.

CSS3 :in-range selector example

<style>
input:in-range {
    border: 1px solid blue;
}
</style>



<input type="number" min="10" max="20" value="15">
<p>The border for this value will be blue</p>

The :in-range CSS pseudo-class matches when an element has its value attribute inside the specified range limitations for this element. It allows the page to give a feedback that the value currently defined using the element is inside the range limits.[1]

Child Pseudo Class

“The :nth-child(an+b) CSS pseudo-class matches an element that has an+b-1 siblings before it in the document tree, for a given positive or zero value for n” - MDN :nth-child

Select element using its ID without the high specificity of the ID selector

This trick helps you select an element using the ID as a value for an attribute selector to avoid the high specificity of the ID selector.

HTML:

<div id="element">...</div>  

CSS

#element { ... } /* High specificity will override many selectors */

[id="element"] { ... } /* Low specificity, can be overridden easily */

A. The :not pseudo-class example & B. :focus-within CSS pseudo-class

A. The syntax is presented above.

The following selector matches all <input> elements in an HTML document that are not disabled and don’t have the class .example:

HTML:

<form>
    Phone: <input type="tel" class="example">
    E-mail: <input type="email" disabled="disabled">
    Password: <input type="password">
</form>

CSS:

input:not([disabled]):not(.example){
   background-color: #ccc;
}

The :not() pseudo-class will also support comma-separated selectors in Selectors Level 4:

CSS:

input:not([disabled], .example){
   background-color: #ccc;
}

Live Demo on JSBin

See background syntax here.

B. The :focus-within CSS pseudo-class

HTML:

  <h3>Background is blue if the input is focused .</p>
  <div>
    <input type="text">
  </div>

CSS:

div {
  height: 80px;
}
input{
  margin:30px;
}
div:focus-within {
  background-color: #1565C0;
}

The :only-child pseudo-class selector example

The :only-child CSS pseudo-class represents any element which is the only child of its parent.

HTML:

<div>
  <p>This paragraph is the only child of the div, it will have the color blue</p>
</div>

<div>
  <p>This paragraph is one of the two children of the div</p>
  <p>This paragraph is one of the two children of its parent</p>
</div>

CSS:

p:only-child {
  color: blue;
}

The above example selects the <p> element that is the unique child from its parent, in this case a <div>.

Live Demo on JSBin

The :last-of-type selector

The :last-of-type selects the element that is the last child, of a particular type, of its parent. In the example below, the css selects the last paragraph and the last heading h1.

p:last-of-type { 
  background: #C5CAE9; 
}
h1:last-of-type { 
  background: #CDDC39; 
}

<div class="container">
    <p>First paragraph</p>
    <p>Second paragraph</p>
    <p>Last paragraph</p>
    <h1>Heading 1</h1>
    <h2>First heading 2</h2>
    <h2>Last heading 2</h2>
</div>

jsFiddle