What is the Difference Between Single and Double Colon in CSS?

What is the Difference Between Single and Double Colon in CSS?

Ferenc Almasi β€’ πŸ”„ 2020 November 04 β€’ πŸ“– 2 min read

Do you know what is the difference between single and double colon in CSS? Or did you know that there is a difference at all?

/* CSS3 syntax */
.css3::before { ... },
.css3::after  { ... }

/* CSS2 syntax */
.css2:before { ... },
.css2:after  { ... }
double-vs-single.css
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Single is used for pseudo-classes like :active or :hover, while double is used for pseudo-elements like ::before or ::after. So what is the difference between pseudo-classes and pseudo-elements?

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Pseudo-classes

Pseudo-classes as used for selecting states of an element. They are not elements themselves. Some examples are:

.anchor:hover {
    /* styles for the hover state of the anchor */
}

.anchor:visited {
   /* styles for already visited anchor */
}
pseudo-classes.css
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Pseudo-elements

pseudo-elements on the other hand are used for selecting parts of an actual DOM element, such as what comes before or after it, specific letters, or even lines. Some examples are:

.paragraph::before {
    /* style the pseudo element before the paragraph */
}

.paragraph::after {
    /* style the pseudo element after the paragraph */
}

.paragraph::first-line {
    /* style the first line of the paragraph */
}

.paragraph::first-letter {
    /* style the first letter of the paragraph */
}
pseudo-elements.css
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What is the difference between sing and double colon in CSS?
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