Hey there, today I picked the topic CSS Pseudo-elements and Pseudo-classes, You may ask why? it's because I little bit confused with the pseudo-elements and pseudo-class. So I just want to make clear about this today and thought to share my learnings here.

Pseudo-elements and Pseudo-classes are some of the cool concepts of CSS. So learning it will surely help you when you want to design with CSS.

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So what is Pseudo-element?

A CSS pseudo-element is used to style specified parts of an element.

For example, it can be used to:

• Style the first letter, or line, of an element
• Insert content before, or after, the content of an element

Syntax

The syntax of pseudo-elements:

selector::pseudo-element {
  property: value;
}

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And what are Pseudo-classes?

A pseudo-class is used to define a special state of an element.

For example, it can be used to:

• Style an element when a user mouses over it
• Style visited and unvisited links differently
• Style an element when it gets focus

Syntax

The syntax of pseudo-classes:

selector:pseudo-class {
  property: value;
}

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Can you find the difference in syntax?

Notice the double colon notation - ::first-line versus :first-line

The single-colon notation for pseudo-classes and double-colon notation used for pseudo-elements in CSS3.

This was an attempt from W3C to distinguish between pseudo-classes and pseudo-elements.

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Examples of CSS Pseudo Elements

Selector	Example	Description
::after	p::after	Insert something after the content of each <p> element
::before	p::before	Insert something before the content of each <p> element
::first-letter	p::first-letter	Selects the first letter of each <p> element
::first-line	p::first-line	Selects the first line of each <p> element
::marker	::marker	Selects the markers of list items
::selection	p::selection	Selects the portion of an element that is selected by a user

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Examples of CSS Pseudo Classes

Selector	Example	Example description
:active	a:active	Selects the active link
:checked	input:checked	Selects every checked <input> element
:disabled	input:disabled	Selects every disabled <input> element
:empty	p:empty	Selects every <p> element that has no children
:enabled	input:enabled	Selects every enabled <input> element
:first-child	p:first-child	Selects every <p> elements that is the first child of its parent
:first-of-type	p:first-of-type	Selects every <p> element that is the first <p> element of its parent
:focus	input:focus	Selects the <input> element that has focus
:hover	a:hover	Selects links on mouse over
:in-range	input:in-range	Selects <input> elements with a value within a specified range
:invalid	input:invalid	Selects all <input> elements with an invalid value
:lang(language)	p:lang(it)	Selects every <p> element with a lang attribute value starting with "it"
:last-child	p:last-child	Selects every <p> elements that is the last child of its parent
:last-of-type	p:last-of-type	Selects every <p> element that is the last <p> element of its parent
:link	a:link	Selects all unvisited links
:not(selector)	:not(p)	Selects every element that is not a <p> element
:nth-child(n)	p:nth-child(2)	Selects every <p> element that is the second child of its parent
:nth-last-child(n)	p:nth-last-child(2)	Selects every <p> element that is the second child of its parent, counting from the last child
:nth-last-of-type(n)	p:nth-last-of-type(2)	Selects every <p> element that is the second <p> element of its parent, counting from the last child
:nth-of-type(n)	p:nth-of-type(2)	Selects every <p> element that is the second <p> element of its parent
:only-of-type	p:only-of-type	Selects every <p> element that is the only <p> element of its parent
:only-child	p:only-child	Selects every <p> element that is the only child of its parent
:optional	input:optional	Selects <input> elements with no "required" attribute
:out-of-range	input:out-of-range	Selects <input> elements with a value outside a specified range
:read-only	input:read-only	Selects <input> elements with a "readonly" attribute specified
:read-write	input:read-write	Selects <input> elements with no "readonly" attribute
:required	input:required	Selects <input> elements with a "required" attribute specified
:root	root	Selects the document's root element
:target	#news:target	Selects the current active #news element (clicked on a URL containing that anchor name)
:valid	input:valid	Selects all <input> elements with a valid value
:visited	a:visited	Selects all visited links

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References

1. https://www.w3schools.com/css/css_pseudo_elements.asp
2. https://www.w3schools.com/css/css_pseudo_classes.asp
3. https://developer.mozilla.org/en-US/docs/Learn/CSS/Building_blocks/Selectors/Pseudo-classes_and_pseudo-elements

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Hope you get an idea about pseudo-elements and pseudo-classes. Thanks for taking your time and read this article. If you found this article useful follow me on Twitter. Feel free to contact me anytime to discuss or share your ideas.