Css pseudo after element

Pseudo-classes and pseudo-elements

The next set of selectors we will look at are referred to as pseudo-classes and pseudo-elements. There are a large number of these, and they often serve quite specific purposes. Once you know how to use them, you can look at the list to see if there is something which works for the task you are trying to achieve. Once again the relevant MDN page for each selector is helpful in explaining browser support.

Prerequisites:	Basic computer literacy, basic software installed, basic knowledge of working with files, HTML basics (study Introduction to HTML), and an idea of how CSS works (study CSS first steps).
Objective:	To learn about the pseudo-class and pseudo-element selectors.

What is a pseudo-class?

A pseudo-class is a selector that selects elements that are in a specific state, e.g. they are the first element of their type, or they are being hovered over by the mouse pointer. They tend to act as if you had applied a class to some part of your document, often helping you cut down on excess classes in your markup, and giving you more flexible, maintainable code.

Pseudo-classes are keywords that start with a colon. For example, :hover is a pseudo-class.

Simple pseudo-class example

Let’s look at a simple example. If we wanted to make the first paragraph in an article larger and bold, we could add a class to that paragraph and then add CSS to that class, as shown in the first example below:

However, this could be annoying to maintain — what if a new paragraph got added to the top of the document? We’d need to move the class over to the new paragraph. Instead of adding the class, we could use the :first-child pseudo-class selector — this will always target the first child element in the article, and we will no longer need to edit the HTML (this may not always be possible anyway, maybe due to it being generated by a CMS).

All pseudo-classes behave in this same kind of way. They target some bit of your document that is in a certain state, behaving as if you had added a class into your HTML. Take a look at some other examples on MDN:

Note: It is valid to write pseudo-classes and elements without any element selector preceding them. In the example above, you could write :first-child and the rule would apply to any element that is the first child of an element, not just a paragraph first child — :first-child is equivalent to *:first-child . However, usually you want more control than that, so you need to be more specific.

User-action pseudo classes

Some pseudo-classes only apply when the user interacts with the document in some way. These user-action pseudo-classes, sometimes referred to as dynamic pseudo-classes, act as if a class had been added to the element when the user interacts with it. Examples include:

• :hover — mentioned above; this only applies if the user moves their pointer over an element, typically a link.
• :focus — only applies if the user focuses the element by clicking or using keyboard controls.

What is a pseudo-element?

Pseudo-elements behave in a similar way. However, they act as if you had added a whole new HTML element into the markup, rather than applying a class to existing elements.

Pseudo-elements start with a double colon :: . ::before is an example of a pseudo-element.

Note: Some early pseudo-elements used the single colon syntax, so you may sometimes see this in code or examples. Modern browsers support the early pseudo-elements with single- or double-colon syntax for backwards compatibility.

For example, if you wanted to select the first line of a paragraph you could wrap it in a element and use an element selector; however, that would fail if the number of words you had wrapped were longer or shorter than the parent element’s width. As we tend not to know how many words will fit on a line — as that will change if the screen width or font-size changes — it is impossible to robustly do this by adding HTML.

The ::first-line pseudo-element selector will do this for you reliably — if the number of words increases or decreases it will still only select the first line.

It acts as if a was magically wrapped around that first formatted line, and updated each time the line length changed.

You can see that this selects the first line of both paragraphs.

Combining pseudo-classes and pseudo-elements

If you wanted to make the first line of the first paragraph bold you could chain the :first-child and ::first-line selectors together. Try editing the previous live example so it uses the following CSS. We are saying that we want to select the first line, of the first

element, which is inside an element.

article p:first-child::first-line  font-size: 120%; font-weight: bold; > 

Generating content with ::before and ::after

There are a couple of special pseudo-elements, which are used along with the content property to insert content into your document using CSS.

You could use these to insert a string of text, such as in the live example below. Try changing the text value of the content property and see it change in the output. You could also change the ::before pseudo-element to ::after and see the text inserted at the end of the element instead of the beginning.

Inserting strings of text from CSS isn’t really something we do very often on the web however, as that text is inaccessible to some screen readers and might be hard for someone to find and edit in the future.

A more valid use of these pseudo-elements is to insert an icon, for example the little arrow added in the example below, which is a visual indicator that we wouldn’t want read out by a screen reader:

These pseudo-elements are also frequently used to insert an empty string, which can then be styled just like any element on the page.

In this next example, we have added an empty string using the ::before pseudo-element. We have set this to display: block in order that we can style it with a width and height. We then use CSS to style it just like any element. You can play around with the CSS and change how it looks and behaves.

The use of the ::before and ::after pseudo-elements along with the content property is referred to as «Generated Content» in CSS, and you will often see this technique being used for various tasks. A great example is the site CSS Arrow Please, which helps you to generate an arrow with CSS. Look at the CSS as you create your arrow and you will see the ::before and ::after pseudo-elements in use. Whenever you see these selectors, look at the content property to see what is being added to the HTML element.

Summary

In this article we’ve introduced CSS pseudo-classes and pseudo-elements, which are special types of selectors.

Pseudo-classes enable you to target an element when it’s in a particular state, as if you had added a class for that state to the DOM. Pseudo-elements act as if you had added a whole new element to the DOM, and enable you to style that. The ::before and ::after pseudo-elements enable you to insert content into the document using CSS.

In the next article, we’ll learn about combinators.

See also

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::after

In CSS, ::after creates a pseudo-element that is the last child of the selected element. It is often used to add cosmetic content to an element with the content property. It is inline by default.

Try it

Note: The pseudo-elements generated by ::before and ::after are contained by the element’s formatting box, and thus don’t apply to replaced elements such as , or to elements.

Syntax

Note: CSS introduced the ::after notation (with two colons) to distinguish pseudo-classes from pseudo-elements. For backward compatibility, browsers also accept :after , introduced earlier.

Examples

Simple usage

Let’s create two classes: one for boring paragraphs and one for exciting ones. We can use these classes to add pseudo-elements to the end of paragraphs.

HTML

p class="boring-text">Here is some plain old boring text.p> p>Here is some normal text that is neither boring nor exciting.p> p class="exciting-text">Contributing to MDN is easy and fun.p> 

CSS

.exciting-text::after  content: " ; color: green; > .boring-text::after  content: " ; color: red; > 

Result

Decorative example

We can style text or images in the content property almost any way we want.

HTML

span class="ribbon">Look at the orange box after this text. span> 

CSS

.ribbon  background-color: #5bc8f7; > .ribbon::after  content: "This is a fancy orange box."; background-color: #ffba10; border-color: black; border-style: dotted; > 

Result

Tooltips

This example uses ::after , in conjunction with the attr() CSS expression and a data-descr custom data attribute, to create tooltips. No JavaScript is required!

We can also support keyboard users with this technique, by adding a tabindex of 0 to make each span keyboard focusable, and using a CSS :focus selector. This shows how flexible ::before and ::after can be, though for the most accessible experience a semantic disclosure widget created in some other way (such as with details and summary elements) is likely to be more appropriate.

HTML

p> Here we have some span tabindex="0" data-descr="collection of words and punctuation"> text span> with a few span tabindex="0" data-descr="small popups that appear when hovering"> tooltipsspan >. p> 

CSS

span[data-descr]  position: relative; text-decoration: underline; color: #00f; cursor: help; > span[data-descr]:hover::after, span[data-descr]:focus::after  content: attr(data-descr); position: absolute; left: 0; top: 24px; min-width: 200px; border: 1px #aaaaaa solid; border-radius: 10px; background-color: #ffffcc; padding: 12px; color: #000000; font-size: 14px; z-index: 1; > 

Result

Accessibility concerns

Using an ::after pseudo-element to add content is discouraged, as it is not reliably accessible to screen readers.

Specifications

Browser compatibility

BCD tables only load in the browser

See also

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Pseudo-elements

A CSS pseudo-element is a keyword added to a selector that lets you style a specific part of the selected element(s).

Syntax

selector::pseudo-element  property: value; > 

For example, ::first-line can be used to change the font of the first line of a paragraph.

/* The first line of every 
element. */ p::first-line  color: blue; text-transform: uppercase; > 

Double colons ( :: ) are used for pseudo-elements. This distinguishes pseudo-elements from pseudo-classes that use single colon ( : ) in their notation.

You can use only one pseudo-element in a selector. The pseudo-element must appear after all the other components in the complex or compound selector in which it appears. For example, you can select a paragraph’s first line using p::first-line but not the first-line’s children or a hovered first line. So both p::first-line > * and p::first-line:hover are invalid.

While it is not possible to select an element based on its state by using pseudo-elements, a pseudo-element can be used to select and style a part of an element that already has a state applied to it. For example, p:hover::first-line selects the first line (pseudo-element) of a paragraph when the paragraph itself is being hovered (pseudo-class).

Note: When a selector list contains an invalid selector, the entire style block is ignored.

List of pseudo-elements

Pseudo-elements defined by a set of CSS specifications include the following:

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