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In CSS, ::before
creates a pseudo-element that is the first 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.
/* Add a heart before links */ a::before { content: "
♥"; }
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 <img>
, or to <br>
elements.
Syntax
/* CSS3 syntax */ ::before /* CSS2 syntax */ :before
Note: CSS3 introduced the ::before
notation (with two colons) to distinguish pseudo-classes from pseudo-elements. Browsers also accept :before
, introduced in CSS2.
Examples
Adding quotation marks
One simple example of using ::before
pseudo-elements is to provide quotation marks. Here we use both ::before
and
to insert quotation characters.::after
HTML
<q>Some quotes,</q> he said, <q>are better than none.</q>
CSS
q::before { content: "«"; color: blue; } q::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">Notice where the orange box is.</span>
CSS
.ribbon { background-color: #5BC8F7; } .ribbon::before { content: "Look at this orange box."; background-color: #FFBA10; border-color: black; border-style: dotted; }
Result
To-do list
In this example we will create a simple to-do list using pseudo-elements. This method can often be used to add small touches to the UI and improve user experience.
HTML
<ul> <li>Buy milk</li> <li>Take the dog for a walk</li> <li>Exercise</li> <li>Write code</li> <li>Play music</li> <li>Relax</li> </ul>
CSS
li { list-style-type: none; position: relative; margin: 2px; padding: 0.5em 0.5em 0.5em 2em; background: lightgrey; font-family: sans-serif; } li.done { background: #CCFF99; } li.done::before { content: ''; position: absolute; border-color: #009933; border-style: solid; border-width: 0 0.3em 0.25em 0; height: 1em; top: 1.3em; left: 0.6em; margin-top: -1em; transform: rotate(45deg); width: 0.5em; }
JavaScript
var list = document.querySelector('ul'); list.addEventListener('click', function(ev) { if (ev.target.tagName === 'LI') { ev.target.classList.toggle('done'); } }, false);
Here is the above code example running live. Note that there are no icons used, and the check-mark is actually the ::before
that has been styled in CSS. Go ahead and get some stuff done.
Result
Notes
Although the positioning fixes in Firefox 3.5 do not allow content to be generated as a separate previous sibling (as per the CSS spec stating "The :before and :after pseudo-elements elements interact with other boxes... as if they were real elements inserted just inside their associated element."), they can be used to provide a slight improvement on tableless layouts (e.g., to achieve centering) in that, as long as the content to be centered is wrapped in a further child, a column before and after the content can be introduced without adding a previous or following sibling (i.e., it is perhaps more semantically correct to add an additional span as below, than it would to add an empty <div/> before and after). (And always remember to add a width to a float, since, otherwise, it will not float!)
HTML
<div class="example"> <span id="floatme">"Floated Before" should be generated on the left of the viewport and not allow overflow in this line to flow under it. Likewise should "Floated After" appear on the right of the viewport and not allow this line to flow under it.</span> </div>
CSS
#floatme { float: left; width: 50%; } /* To get an empty column, just indicate a hex code for a non-breaking space: \a0 as the content (use \0000a0 when following such a space with other characters) */ .example::before { content: "Floated Before"; float: left; width: 25%; } .example::after { content: "Floated After"; float: right; width: 25%; } /* For styling */ .example::before, .example::after { background: yellow; color: red; }
Result
Specifications
Specification | Status | Comment |
---|---|---|
CSS Pseudo-Elements Level 4 The definition of '::before' in that specification. |
Working Draft | No significant changes to the previous specification. |
CSS Transitions | Working Draft | Allows transitions on properties defined on pseudo-elements. |
CSS Animations | Working Draft | Allows animations on properties defined on pseudo-elements. |
Selectors Level 3 The definition of '::before' in that specification. |
Recommendation | Introduces the two-colon syntax. |
CSS Level 2 (Revision 1) The definition of '::before' in that specification. |
Recommendation | Initial definition, using the one-colon syntax |
Browser compatibility
Desktop | Mobile | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Basic support | Chrome
Full support
Yes
| Edge
Full support
Yes
| Firefox
Full support
1.5
| IE
Full support
9
| Opera
Full support
7
| Safari
Full support
4
| WebView Android
Full support
Yes
| Chrome Android
Full support
Yes
| Edge Mobile
Full support
Yes
| Firefox Android
Full support
Yes
| Opera Android ? | Safari iOS Full support 5.1 | Samsung Internet Android Full support Yes |
Animation and transition support | Chrome Full support 26 | Edge Full support Yes | Firefox Full support 4 | IE No support No | Opera No support No | Safari No support No | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android No support No | Safari iOS No support No | Samsung Internet Android Full support Yes |
Legend
- Full support
- Full support
- No support
- No support
- Compatibility unknown
- Compatibility unknown
- See implementation notes.
- See implementation notes.
- Uses a non-standard name.
- Uses a non-standard name.