30 Seconds of CSS

A curated collection of useful CSS snippets you can understand in 30 seconds or less. Inspired by 30 seconds of code.

View online

https://css.30secondsofcode.org

Contributing

See CONTRIBUTING.md for the snippet template.

Related projects

Animation

View contents

Bouncing loader
Button border animation
Donut spinner
Easing variables
Height transition
Hover shadow box animation
Hover underline animation

Interactivity

View contents

Disable selection
Popout menu
Sibling fade

Layout

View contents

Box-sizing reset
Clearfix
Constant width to height ratio
Display table centering
Evenly distributed children
Fit image in container
Flexbox centering
Ghost trick
Grid centering
Last item with remaining available height
Offscreen
Transform centering
Truncate text multiline
Truncate text

Other

View contents

Calc()
Custom variables

Visual

View contents

Circle
Counter
Custom scrollbar
Custom text selection
Dynamic shadow
Etched text
Focus Within
Fullscreen
Gradient text
Hairline border
Mouse cursor gradient tracking
:not selector
Overflow scroll gradient
Pretty text underline
Reset all styles
Shape separator
System font stack
Toggle switch
Triangle
Zebra striped list

Animation

Bouncing loader

Creates a bouncing loader animation.

<div class="bouncing-loader">
  <div></div>
  <div></div>
  <div></div>
</div>

@keyframes bouncing-loader {
  to {
    opacity: 0.1;
    transform: translate3d(0, -1rem, 0);
  }
}
.bouncing-loader {
  display: flex;
  justify-content: center;
}
.bouncing-loader > div {
  width: 1rem;
  height: 1rem;
  margin: 3rem 0.2rem;
  background: #8385aa;
  border-radius: 50%;
  animation: bouncing-loader 0.6s infinite alternate;
}
.bouncing-loader > div:nth-child(2) {
  animation-delay: 0.2s;
}
.bouncing-loader > div:nth-child(3) {
  animation-delay: 0.4s;
}

Explanation

Note: 1rem is usually 16px.

@keyframes defines an animation that has two states, where the element changes opacity and is translated up on the 2D plane using transform: translate3d(). Using a single axis translation on transform: translate3d() improves the performance of the animation.
.bouncing-loader is the parent container of the bouncing circles and uses display: flex and justify-content: center to position them in the center.
.bouncing-loader > div, targets the three child divs of the parent to be styled. The divs are given a width and height of 1rem, using border-radius: 50% to turn them from squares to circles.
margin: 3rem 0.2rem specifies that each circle has a top/bottom margin of 3rem and left/right margin of 0.2rem so that they do not directly touch each other, giving them some breathing room.
animation is a shorthand property for the various animation properties: animation-name, animation-duration, animation-iteration-count, animation-direction are used.
nth-child(n) targets the element which is the nth child of its parent.
animation-delay is used on the second and third div respectively, so that each element does not start the animation at the same time.

Browser support

100.0%

https://caniuse.com/#feat=css-animation

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Button border animation

Creates a border animation on hover.

<div class="button-border"><button class="button">Submit</button></div>

.button {
  background-color: #c47135;
  border: none;
  color: #ffffff;
  outline: none;
  padding: 12px 40px 10px;
  position: relative;
}
.button:before,
.button:after {
  border: 0 solid transparent;
  transition: all 0.25s;
  content: '';
  height: 24px;
  position: absolute;
  width: 24px;
}
.button:before {
  border-top: 2px solid #c47135;
  left: 0px;
  top: -5px;
}
.button:after {
  border-bottom: 2px solid #c47135;
  bottom: -5px;
  right: 0px;
}
.button:hover {
  background-color: #c47135;
}
.button:hover:before,
.button:hover:after {
  height: 100%;
  width: 100%;
}

Explanation

Use the :before and :after pseduo-elements as borders that animate on hover.

Browser support

100.0%

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Donut spinner

Creates a donut spinner that can be used to indicate the loading of content.

<div class="donut"></div>

@keyframes donut-spin {
  0% {
    transform: rotate(0deg);
  }
  100% {
    transform: rotate(360deg);
  }
}
.donut {
  display: inline-block;
  border: 4px solid rgba(0, 0, 0, 0.1);
  border-left-color: #7983ff;
  border-radius: 50%;
  width: 30px;
  height: 30px;
  animation: donut-spin 1.2s linear infinite;
}

Explanation

Use a semi-transparent border for the whole element, except one side that will serve as the loading indicator for the donut. Use animation to rotate the element.

Browser support

100.0%

⚠️ Requires prefixes for full support.

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Easing variables

Variables that can be reused for transition-timing-function properties, more powerful than the built-in ease, ease-in, ease-out and ease-in-out.

<div class="easing-variables">Hover</div>

:root {
  /* Place variables in here to use globally */
}

.easing-variables {
  --ease-in-quad: cubic-bezier(0.55, 0.085, 0.68, 0.53);
  --ease-in-cubic: cubic-bezier(0.55, 0.055, 0.675, 0.19);
  --ease-in-quart: cubic-bezier(0.895, 0.03, 0.685, 0.22);
  --ease-in-quint: cubic-bezier(0.755, 0.05, 0.855, 0.06);
  --ease-in-expo: cubic-bezier(0.95, 0.05, 0.795, 0.035);
  --ease-in-circ: cubic-bezier(0.6, 0.04, 0.98, 0.335);

  --ease-out-quad: cubic-bezier(0.25, 0.46, 0.45, 0.94);
  --ease-out-cubic: cubic-bezier(0.215, 0.61, 0.355, 1);
  --ease-out-quart: cubic-bezier(0.165, 0.84, 0.44, 1);
  --ease-out-quint: cubic-bezier(0.23, 1, 0.32, 1);
  --ease-out-expo: cubic-bezier(0.19, 1, 0.22, 1);
  --ease-out-circ: cubic-bezier(0.075, 0.82, 0.165, 1);

  --ease-in-out-quad: cubic-bezier(0.455, 0.03, 0.515, 0.955);
  --ease-in-out-cubic: cubic-bezier(0.645, 0.045, 0.355, 1);
  --ease-in-out-quart: cubic-bezier(0.77, 0, 0.175, 1);
  --ease-in-out-quint: cubic-bezier(0.86, 0, 0.07, 1);
  --ease-in-out-expo: cubic-bezier(1, 0, 0, 1);
  --ease-in-out-circ: cubic-bezier(0.785, 0.135, 0.15, 0.86);
  display: inline-block;
  width: 75px;
  height: 75px;
  padding: 10px;
  color: white;
  line-height: 50px;
  text-align: center;
  background: #333;
  transition: transform 1s var(--ease-out-quart);
}

.easing-variables:hover {
  transform: rotate(45deg);
}

Explanation

The variables are defined globally within the :root CSS pseudo-class which matches the root element of a tree representing the document.
In HTML, :root represents the <html> element and is identical to the selector html, except that its specificity is higher.

Browser support

96.5%

https://caniuse.com/#feat=css-variables

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Height transition

Transitions an element's height from 0 to auto when its height is unknown.

<div class="trigger">
  Hover me to see a height transition.
  <div class="el">content</div>
</div>

.el {
  transition: max-height 0.5s;
  overflow: hidden;
  max-height: 0;
}

.trigger:hover > .el {
  max-height: var(--max-height);
}

var el = document.querySelector('.el')
var height = el.scrollHeight
el.style.setProperty('--max-height', height + 'px')

Explanation

transition: max-height: 0.5s cubic-bezier(...) specifies that changes to max-height should be transitioned over 0.5 seconds, using an ease-out-quint timing function.
overflow: hidden prevents the contents of the hidden element from overflowing its container.
max-height: 0 specifies that the element has no height initially.
.target:hover > .el specifies that when the parent is hovered over, target a child .el within it and use the --max-height variable which was defined by JavaScript.

el.scrollHeight is the height of the element including overflow, which will change dynamically based on the content of the element.
el.style.setProperty(...) sets the --max-height CSS variable which is used to specify the max-height of the element the target is hovered over, allowing it to transition smoothly from 0 to auto.

Browser support

96.5%

Requires JavaScript

⚠️ Causes reflow on each animation frame, which will be laggy if there are a large number of elements beneath the element that is transitioning in height.

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Hover shadow box animation

Creates a shadow box around the text when it is hovered.

<p class="hover-shadow-box-animation">Box it!</p>

.hover-shadow-box-animation {
  display: inline-block;
  vertical-align: middle;
  transform: perspective(1px) translateZ(0);
  box-shadow: 0 0 1px transparent;
  margin: 10px;
  transition-duration: 0.3s;
  transition-property: box-shadow, transform;
}
.hover-shadow-box-animation:hover,
.hover-shadow-box-animation:focus,
.hover-shadow-box-animation:active {
  box-shadow: 1px 10px 10px -10px rgba(0, 0, 24, 0.5);
  transform: scale(1.2);
}

Explanation

display: inline-block to set width and length for p element thus making it an inline-block.
Set transform: perspective(1px) to give element a 3D space by affecting the distance between the Z plane and the user and translate(0) to reposition the p element along z-axis in 3D space.
box-shadow: to set up the box.
transparent to make box transparent.
transition-property to enable transitions for both box-shadow and transform.
:hover to activate whole css when hovering is done until active.
transform: scale(1.2) to change the scale, magnifying the text.

Browser support

100.0%

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Hover underline animation

Creates an animated underline effect when the text is hovered over.

Credit: https://flatuicolors.com/

<p class="hover-underline-animation">Hover this text to see the effect!</p>

.hover-underline-animation {
  display: inline-block;
  position: relative;
  color: #0087ca;
}
.hover-underline-animation::after {
  content: '';
  position: absolute;
  width: 100%;
  transform: scaleX(0);
  height: 2px;
  bottom: 0;
  left: 0;
  background-color: #0087ca;
  transform-origin: bottom right;
  transition: transform 0.25s ease-out;
}
.hover-underline-animation:hover::after {
  transform: scaleX(1);
  transform-origin: bottom left;
}

Explanation

display: inline-block makes the block p an inline-block to prevent the underline from spanning the entire parent width rather than just the content (text).
position: relative on the element establishes a Cartesian positioning context for pseudo-elements.
::after defines a pseudo-element.
position: absolute takes the pseudo element out of the flow of the document and positions it in relation to the parent.
width: 100% ensures the pseudo-element spans the entire width of the text block.
transform: scaleX(0) initially scales the pseudo element to 0 so it has no width and is not visible.
bottom: 0 and left: 0 position it to the bottom left of the block.
transition: transform 0.25s ease-out means changes to transform will be transitioned over 0.25 seconds with an ease-out timing function.
transform-origin: bottom right means the transform anchor point is positioned at the bottom right of the block.
:hover::after then uses scaleX(1) to transition the width to 100%, then changes the transform-origin to bottom left so that the anchor point is reversed, allowing it transition out in the other direction when hovered off.

Browser support

100.0%

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Interactivity

Disable selection

Makes the content unselectable.

<p>You can select me.</p>
<p class="unselectable">You can't select me!</p>

.unselectable {
  user-select: none;
}

Explanation

user-select: none specifies that the text cannot be selected.

Browser support

97.5%

⚠️ Requires prefixes for full support.
⚠️ This is not a secure method to prevent users from copying content.

https://caniuse.com/#feat=user-select-none

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Popout menu

Reveals an interactive popout menu on hover and focus.

<div class="reference" tabindex="0"><div class="popout-menu">Popout menu</div></div>

.reference {
  position: relative;
  background: tomato;
  width: 100px;
  height: 100px;
}
.popout-menu {
  position: absolute;
  visibility: hidden;
  left: 100%;
  background: #333;
  color: white;
  padding: 15px;
}
.reference:hover > .popout-menu,
.reference:focus > .popout-menu,
.reference:focus-within > .popout-menu {
  visibility: visible;
}

Explanation

position: relative on the reference parent establishes a Cartesian positioning context for its child.
position: absolute takes the popout menu out of the flow of the document and positions it in relation to the parent.
left: 100% moves the the popout menu 100% of its parent's width from the left.
visibility: hidden hides the popout menu initially and allows for transitions (unlike display: none).
.reference:hover > .popout-menu means that when .reference is hovered over, select immediate children with a class of .popout-menu and change their visibility to visible, which shows the popout.
.reference:focus > .popout-menu means that when .reference is focused, the popout would be shown.
.reference:focus-within > .popout-menu ensures that the popout is shown when the focus is within the reference.

Browser support

100.0%

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Sibling fade

Fades out the siblings of a hovered item.

<div class="sibling-fade">
  <span>Item 1</span> <span>Item 2</span> <span>Item 3</span> <span>Item 4</span>
  <span>Item 5</span> <span>Item 6</span>
</div>

span {
  padding: 0 1rem;
  transition: opacity 0.2s;
}

.sibling-fade:hover span:not(:hover) {
  opacity: 0.5;
}

Explanation

transition: opacity 0.2s specifies that changes to opacity will be transitioned over 0.2 seconds.
.sibling-fade:hover span:not(:hover) specifies that when the parent is hovered, select any span children that are not currently being hovered and change their opacity to 0.5.

Browser support

100.0%

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Layout

Box-sizing reset

Resets the box-model so that widths and heights are not affected by their borders or padding.

<div class="box">border-box</div>
<div class="box content-box">content-box</div>

html {
  box-sizing: border-box;
}
*,
*::before,
*::after {
  box-sizing: inherit;
}
.box {
  display: inline-block;
  width: 150px;
  height: 150px;
  padding: 10px;
  background: tomato;
  color: white;
  border: 10px solid red;
}
.content-box {
  box-sizing: content-box;
}

Explanation

box-sizing: border-box makes the addition of padding or borders not affect an element's width or height.
box-sizing: inherit makes an element respect its parent's box-sizing rule.

Browser support

100.0%

https://caniuse.com/#feat=css3-boxsizing

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Clearfix

Ensures that an element self-clears its children.

Note: This is only useful if you are still using float to build layouts. Please consider using a modern approach with flexbox layout or grid layout.

<div class="clearfix">
  <div class="floated">float a</div>
  <div class="floated">float b</div>
  <div class="floated">float c</div>
</div>

.clearfix::after {
  content: '';
  display: block;
  clear: both;
}

.floated {
  float: left;
}

Explanation

.clearfix::after defines a pseudo-element.
content: '' allows the pseudo-element to affect layout.
clear: both indicates that the left, right or both sides of the element cannot be adjacent to earlier floated elements within the same block formatting context.

Browser support

100.0%

⚠️ For this snippet to work properly you need to ensure that there are no non-floating children in the container and that there are no tall floats before the clearfixed container but in the same formatting context (e.g. floated columns).

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Constant width to height ratio

Given an element of variable width, it will ensure its height remains proportionate in a responsive fashion (i.e., its width to height ratio remains constant).

<div class="constant-width-to-height-ratio"></div>

.constant-width-to-height-ratio {
  background: #333;
  width: 50%;
}
.constant-width-to-height-ratio::before {
  content: '';
  padding-top: 100%;
  float: left;
}
.constant-width-to-height-ratio::after {
  content: '';
  display: block;
  clear: both;
}

Explanation

padding-top on the ::before pseudo-element causes the height of the element to equal a percentage of its width. 100% therefore means the element's height will always be 100% of the width, creating a responsive square.
This method also allows content to be placed inside the element normally.

Browser support

100.0%

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Display table centering

Vertically and horizontally centers a child element within its parent element using display: table (as an alternative to flexbox).

<div class="container">
  <div class="center"><span>Centered content</span></div>
</div>

.container {
  border: 1px solid #333;
  height: 250px;
  width: 250px;
}

.center {
  display: table;
  height: 100%;
  width: 100%;
}

.center > span {
  display: table-cell;
  text-align: center;
  vertical-align: middle;
}

Explanation

display: table on '.center' allows the element to behave like a <table> HTML element.
100% height and width on '.center' allows the element to fill the available space within its parent element.
display: table-cell on '.center > span' allows the element to behave like an HTML element.
text-align: center on '.center > span' centers the child element horizontally.
vertical-align: middle on '.center > span' centers the child element vertically.

The outer parent ('.container' in this case) must have a fixed height and width.

Browser support

100.0%

https://caniuse.com/#search=display%3A%20table

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Evenly distributed children

Evenly distributes child elements within a parent element.

<div class="evenly-distributed-children">
  <p>Item1</p>
  <p>Item2</p>
  <p>Item3</p>
</div>

.evenly-distributed-children {
  display: flex;
  justify-content: space-between;
}

Explanation

display: flex enables flexbox.
justify-content: space-between evenly distributes child elements horizontally. The first item is positioned at the left edge, while the last item is positioned at the right edge.

Alternatively, use justify-content: space-around to distribute the children with space around them, rather than between them.

Browser support

100.0%

⚠️ Needs prefixes for full support.

https://caniuse.com/#feat=flexbox

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Fit image in container

Changes the fit and position of an image within its container while preserving its aspect ratio. Previously only possible using a background image and the background-size property.

<img class="image image-contain" src="https://picsum.photos/600/200" />
<img class="image image-cover" src="https://picsum.photos/600/200" />

.image {
  background: #34495e;
  border: 1px solid #34495e;
  width: 200px;
  height: 200px;
}

.image-contain {
  object-fit: contain;
  object-position: center;
}

.image-cover {
  object-fit: cover;
  object-position: right top;
}

Explanation

object-fit: contain fits the entire image within the container while preserving its aspect ratio.
object-fit: cover fills the container with the image while preserving its aspect ratio.
object-position: [x] [y] positions the image within the container.

Browser support

99.5%

https://caniuse.com/#feat=object-fit

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Flexbox centering

Horizontally and vertically centers a child element within a parent element using flexbox.

<div class="flexbox-centering"><div class="child">Centered content.</div></div>

.flexbox-centering {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100px;
}

Explanation

display: flex enables flexbox.
justify-content: center centers the child horizontally.
align-items: center centers the child vertically.

Browser support

100.0%

⚠️ Needs prefixes for full support.

https://caniuse.com/#feat=flexbox

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Ghost trick

Vertically centers an element in another.

<div class="ghost-trick">
  <div class="ghosting"><p>Vertically centered without changing the position property.</p></div>
</div>

.ghosting {
  height: 300px;
  background: #0ff;
}

.ghosting:before {
  content: '';
  display: inline-block;
  height: 100%;
  vertical-align: middle;
}

p {
  display: inline-block;
  vertical-align: middle;
}

Explanation

Use the style of a :before pseudo-element to vertically align inline elements without changing their position property.

Browser support

100.0%

https://caniuse.com/#feat=inline-block

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Grid centering

Horizontally and vertically centers a child element within a parent element using grid.

<div class="grid-centering"><div class="child">Centered content.</div></div>

.grid-centering {
  display: grid;
  justify-content: center;
  align-items: center;
  height: 100px;
}

Explanation

display: grid enables grid.
justify-content: center centers the child horizontally.
align-items: center centers the child vertically.

Browser support

97.3%

https://caniuse.com/#feat=css-grid

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Last item with remaining available height

Take advantage of available viewport space by giving the last element the remaining available space in current viewport, even when resizing the window.

<div class="container">
  <div>Div 1</div>
  <div>Div 2</div>
  <div>Div 3</div>
</div>

html,
body {
  height: 100%;
  margin: 0;
}

.container {
  height: 100%;
  display: flex;
  flex-direction: column;
}

.container > div:last-child {
  background-color: tomato;
  flex: 1;
}

Explanation

height: 100% set the height of container as viewport height.
display: flex enables flexbox.
flex-direction: column set the direction of flex items' order from top to down.
flex-grow: 1 the flexbox will apply remaining available space of container to last child element.

The parent must have a viewport height. flex-grow: 1 could be applied to the first or second element, which will have all available space.

Browser support

100.0%

⚠️ Needs prefixes for full support.

https://caniuse.com/#feat=flexbox

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Offscreen

A bulletproof way to completely hide an element visually and positionally in the DOM while still allowing it to be accessed by JavaScript and readable by screen readers. This method is very useful for accessibility (ADA) development when more context is needed for visually-impaired users. As an alternative to display: none which is not readable by screen readers or visibility: hidden which takes up physical space in the DOM.

<a class="button" href="http://pantswebsite.com">
  Learn More <span class="offscreen"> about pants</span>
</a>

.offscreen {
  border: 0;
  clip: rect(0 0 0 0);
  height: 1px;
  margin: -1px;
  overflow: hidden;
  padding: 0;
  position: absolute;
  width: 1px;
}

Explanation

Remove all borders.
Use clip to indicate that no part of the element should be shown.
Make the height and width of the element 1px.
Negate the elements height and width using margin: -1px.
Hide the element's overflow.
Remove all padding.
Position the element absolutely so that it does not take up space in the DOM.

Browser support

100.0%

(Although clip technically has been depreciated, the newer clip-path currently has very limited browser support.)

https://caniuse.com/#search=clip

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Transform centering

Vertically and horizontally centers a child element within its parent element using position: absolute and transform: translate() (as an alternative to flexbox or display: table). Similar to flexbox, this method does not require you to know the height or width of your parent or child so it is ideal for responsive applications.

<div class="parent"><div class="child">Centered content</div></div>

.parent {
  border: 1px solid #333;
  height: 250px;
  position: relative;
  width: 250px;
}

.child {
  left: 50%;
  position: absolute;
  top: 50%;
  transform: translate(-50%, -50%);
  text-align: center;
}

Explanation

position: absolute on the child element allows it to be positioned based on its containing block.
left: 50% and top: 50% offsets the child 50% from the left and top edge of its containing block.
transform: translate(-50%, -50%) allows the height and width of the child element to be negated so that it is vertically and horizontally centered.

Note: that the fixed height and width on parent element is for the demo only.

Browser support

100.0%

⚠️ Requires prefix for full support.

https://caniuse.com/#feat=transforms2d

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Truncate text multiline

If the text is longer than one line, it will be truncated for n lines and end with an gradient fade.

<p class="truncate-text-multiline">
  Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut
  labore et.
</p>

.truncate-text-multiline {
  overflow: hidden;
  display: block;
  height: 109.2px;
  margin: 0 auto;
  font-size: 26px;
  line-height: 1.4;
  width: 400px;
  position: relative;
}

.truncate-text-multiline:after {
  content: '';
  position: absolute;
  bottom: 0;
  right: 0;
  width: 150px;
  height: 36.4px;
  background: linear-gradient(to right, rgba(0, 0, 0, 0), #f5f6f9 50%);
}

Explanation

overflow: hidden prevents the text from overflowing its dimensions (for a block, 100% width and auto height).
width: 400px ensures the element has a dimension.
height: 109.2px calculated value for height, it equals font-size * line-height * numberOfLines (in this case 26 * 1.4 * 3 = 109.2)
height: 36.4px calculated value for gradient container, it equals font-size * line-height (in this case 26 * 1.4 = 36.4)
background: linear-gradient(to right, rgba(0, 0, 0, 0), #f5f6f9 50%) gradient from transparent to #f5f6f9

Browser support

100.0%

https://caniuse.com/#feat=css-gradients

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Truncate text

If the text is longer than one line, it will be truncated and end with an ellipsis ….

<p class="truncate-text">If I exceed one line's width, I will be truncated.</p>

.truncate-text {
  overflow: hidden;
  white-space: nowrap;
  text-overflow: ellipsis;
  width: 200px;
}

Explanation

overflow: hidden prevents the text from overflowing its dimensions (for a block, 100% width and auto height).
white-space: nowrap prevents the text from exceeding one line in height.
text-overflow: ellipsis makes it so that if the text exceeds its dimensions, it will end with an ellipsis.
width: 200px; ensures the element has a dimension, to know when to get ellipsis

Browser support

100.0%

⚠️ Only works for single line elements.

https://caniuse.com/#feat=text-overflow

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Other

Calc()

The function calc() allows to define CSS values with the use of mathematical expressions, the value adopted for the property is the result of a mathematical expression.

<div class="box-example"></div>

.box-example {
  height: 280px;
  background: #222 url('https://image.ibb.co/fUL9nS/wolf.png') no-repeat;
  background-position: calc(100% - 20px) calc(100% - 20px);
}

Explanation

It allows addition, subtraction, multiplication and division.
Can use different units (pixel and percent together, for example) for each value in your expression.
It is permitted to nest calc() functions.
It can be used in any property that <length>, <frequency>, <angle>, <time>, <number>, <color>, or <integer> is allowed, like width, height, font-size, top, left, etc.

Browser support

100.0%

https://caniuse.com/#feat=calc

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Custom variables

CSS variables that contain specific values to be reused throughout a document.

<p class="custom-variables">CSS is awesome!</p>

:root {
  /* Place variables within here to use the variables globally. */
}

.custom-variables {
  --some-color: #da7800;
  --some-keyword: italic;
  --some-size: 1.25em;
  --some-complex-value: 1px 1px 2px whitesmoke, 0 0 1em slategray, 0 0 0.2em slategray;
  color: var(--some-color);
  font-size: var(--some-size);
  font-style: var(--some-keyword);
  text-shadow: var(--some-complex-value);
}

Explanation

The variables are defined globally within the :root CSS pseudo-class which matches the root element of a tree representing the document. Variables can also be scoped to a selector if defined within the block.
Declare a variable with --variable-name:.
Reuse variables throughout the document using the var(--variable-name) function.

Browser support

96.5%

https://caniuse.com/#feat=css-variables

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Visual

Circle

Creates a circle shape with pure CSS.

<div class="circle"></div>

.circle {
  border-radius: 50%;
  width: 2rem;
  height: 2rem;
  background: #333;
}

Explanation

border-radius: 50% curves the borders of an element to create a circle.
Since a circle has the same radius at any given point, the width and height must be the same. Differing values will create an ellipse.

Browser support

100.0%

https://caniuse.com/#feat=border-radius

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Counter

Counters are, in essence, variables maintained by CSS whose values may be incremented by CSS rules to track how many times they're used.

<ul>
  <li>List item</li>
  <li>List item</li>
  <li>
    List item
    <ul>
      <li>List item</li>
      <li>List item</li>
      <li>List item</li>
    </ul>
  </li>
</ul>

ul {
  counter-reset: counter;
}

li::before {
  counter-increment: counter;
  content: counters(counter, '.') ' ';
}

Explanation

You can create a ordered list using any type of HTML.

counter-reset Initializes a counter, the value is the name of the counter. By default, the counter starts at 0. This property can also be used to change its value to any specific number.
counter-increment Used in element that will be countable. Once counter-reset initialized, a counter's value can be increased or decreased.
counter(name, style) Displays the value of a section counter. Generally used in a content property. This function can receive two parameters, the first as the name of the counter and the second one can be decimal or upper-roman (decimal by default).
counters(counter, string, style) Displays the value of a section counter. Generally used in a content property. This function can receive three parameters, the first as the name of the counter, the second one you can include a string which comes after the counter and the third one can be decimal or upper-roman (decimal by default).
A CSS counter can be especially useful for making outlined lists, because a new instance of the counter is automatically created in child elements. Using the counters() function, separating text can be inserted between different levels of nested counters.

Browser support

100.0%

https://caniuse.com/#feat=css-counters

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Custom scrollbar

Customizes the scrollbar style for the document and elements with scrollable overflow, on WebKit platforms.

<div class="custom-scrollbar">
  <p>
    Lorem ipsum dolor sit amet consectetur adipisicing elit.<br />
    Iure id exercitationem nulla qui repellat laborum vitae, <br />
    molestias tempora velit natus. Quas, assumenda nisi. <br />
    Quisquam enim qui iure, consequatur velit sit?
  </p>
</div>

.custom-scrollbar {
  height: 70px;
  overflow-y: scroll;
}

/* To style the document scrollbar, remove `.custom-scrollbar` */

.custom-scrollbar::-webkit-scrollbar {
  width: 8px;
}

.custom-scrollbar::-webkit-scrollbar-track {
  box-shadow: inset 0 0 6px rgba(0, 0, 0, 0.3);
  border-radius: 10px;
}

.custom-scrollbar::-webkit-scrollbar-thumb {
  border-radius: 10px;
  box-shadow: inset 0 0 6px rgba(0, 0, 0, 0.5);
}

Explanation

::-webkit-scrollbar targets the whole scrollbar element.
::-webkit-scrollbar-track targets only the scrollbar track.
::-webkit-scrollbar-thumb targets the scrollbar thumb.

There are many other pseudo-elements that you can use to style scrollbars. For more info, visit the WebKit Blog.

Browser support

97.7%

⚠️ Scrollbar styling doesn't appear to be on any standards track.

https://caniuse.com/#feat=css-scrollbar

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Custom text selection

Changes the styling of text selection.

<p class="custom-text-selection">Select some of this text.</p>

::selection {
  background: aquamarine;
  color: black;
}
.custom-text-selection::selection {
  background: deeppink;
  color: white;
}

Explanation

::selection defines a pseudo selector on an element to style text within it when selected. Note that if you don't combine any other selector your style will be applied at document root level, to any selectable element.

Browser support

90.1%

⚠️ Requires prefixes for full support and is not actually in any specification.

https://caniuse.com/#feat=css-selection

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Dynamic shadow

Creates a shadow similar to box-shadow but based on the colors of the element itself.

<div class="dynamic-shadow"></div>

.dynamic-shadow {
  position: relative;
  width: 10rem;
  height: 10rem;
  background: linear-gradient(75deg, #6d78ff, #00ffb8);
  z-index: 1;
}
.dynamic-shadow::after {
  content: '';
  width: 100%;
  height: 100%;
  position: absolute;
  background: inherit;
  top: 0.5rem;
  filter: blur(0.4rem);
  opacity: 0.7;
  z-index: -1;
}

Explanation

position: relative on the element establishes a Cartesian positioning context for psuedo-elements.
z-index: 1 establishes a new stacking context.
::after defines a pseudo-element.
position: absolute takes the pseudo element out of the flow of the document and positions it in relation to the parent.
width: 100% and height: 100% sizes the pseudo-element to fill its parent's dimensions, making it equal in size.
background: inherit causes the pseudo-element to inherit the linear gradient specified on the element.
top: 0.5rem offsets the pseudo-element down slightly from its parent.
filter: blur(0.4rem) will blur the pseudo-element to create the appearance of a shadow underneath.
opacity: 0.7 makes the pseudo-element partially transparent.
z-index: -1 positions the pseudo-element behind the parent but in front of the background.

Browser support

98.5%

⚠️ Requires prefixes for full support.

https://caniuse.com/#feat=css-filters

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Etched text

Creates an effect where text appears to be "etched" or engraved into the background.

<p class="etched-text">I appear etched into the background.</p>

.etched-text {
  text-shadow: 0 2px white;
  font-size: 1.5rem;
  font-weight: bold;
  color: #b8bec5;
}

Explanation

text-shadow: 0 2px white creates a white shadow offset 0px horizontally and 2px vertically from the origin position.
The background must be darker than the shadow for the effect to work.
The text color should be slightly faded to make it look like it's engraved/carved out of the background.

Browser support

100.0%

https://caniuse.com/#feat=css-textshadow

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Focus Within

Changes the appearance of a form if any of its children are focused.

<div class="focus-within">
  <form>
    <label for="given_name">Given Name:</label> <input id="given_name" type="text" /> <br />
    <label for="family_name">Family Name:</label> <input id="family_name" type="text" />
  </form>
</div>

form {
  border: 3px solid #2d98da;
  color: #000000;
  padding: 4px;
}

form:focus-within {
  background: #f7b731;
  color: #000000;
}

Explanation

The psuedo class :focus-within applies styles to a parent element if any child element gets focused. For example, an input element inside a form element.

Browser support

85.4%

⚠️ Not supported in IE11 or the current version of Edge.

https://caniuse.com/#feat=css-focus-within

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Fullscreen

The :fullscreen CSS pseudo-class represents an element that's displayed when the browser is in fullscreen mode.

<div class="container">
  <p><em>Click the button below to enter the element into fullscreen mode. </em></p>
  <div class="element" id="element"><p>I change color in fullscreen mode!</p></div>
  <br />
  <button onclick="var el = document.getElementById('element'); el.requestFullscreen();">
    Go Full Screen!
  </button>
</div>

.container {
  margin: 40px auto;
  max-width: 700px;
}

.element {
  padding: 20px;
  height: 300px;
  width: 100%;
  background-color: skyblue;
  box-sizing: border-box;
}

.element p {
  text-align: center;
  color: white;
  font-size: 3em;
}

.element:-ms-fullscreen p {
  visibility: visible;
}

.element:fullscreen {
  background-color: #e4708a;
  width: 100vw;
  height: 100vh;
}

Explanation

fullscreen CSS pseudo-class selector is used to select and style an element that is being displayed in fullscreen mode.

Browser support

99.1%

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Gradient text

Gives text a gradient color.

<p class="gradient-text">Gradient text</p>

.gradient-text {
  background: -webkit-linear-gradient(pink, red);
  -webkit-text-fill-color: transparent;
  -webkit-background-clip: text;
}

Explanation

background: -webkit-linear-gradient(...) gives the text element a gradient background.
webkit-text-fill-color: transparent fills the text with a transparent color.
webkit-background-clip: text clips the background with the text, filling the text with the gradient background as the color.

Browser support

98.7%

⚠️ Uses non-standard properties.

https://caniuse.com/#feat=text-stroke

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Hairline border

Gives an element a border equal to 1 native device pixel in width, which can look very sharp and crisp.

<div class="hairline-border">text</div>

.hairline-border {
  box-shadow: 0 0 0 1px;
}

@media (min-resolution: 2dppx) {
  .hairline-border {
    box-shadow: 0 0 0 0.5px;
  }
}

@media (min-resolution: 3dppx) {
  .hairline-border {
    box-shadow: 0 0 0 0.33333333px;
  }
}

@media (min-resolution: 4dppx) {
  .hairline-border {
    box-shadow: 0 0 0 0.25px;
  }
}

Explanation

box-shadow, when only using spread, adds a pseudo-border which can use subpixels*.
Use @media (min-resolution: ...) to check the device pixel ratio (1dppx equals 96 DPI), setting the spread of the box-shadow equal to 1 / dppx.

Browser support

100.0%

⚠️ Needs alternate syntax and JavaScript user agent checking for full support.

*Chrome does not support subpixel values on border. Safari does not support subpixel values on box-shadow. Firefox supports subpixel values on both.

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Mouse cursor gradient tracking

A hover effect where the gradient follows the mouse cursor.

Credit: Tobias Reich

<button class="mouse-cursor-gradient-tracking"><span>Hover me</span></button>

.mouse-cursor-gradient-tracking {
  position: relative;
  background: #7983ff;
  padding: 0.5rem 1rem;
  font-size: 1.2rem;
  border: none;
  color: white;
  cursor: pointer;
  outline: none;
  overflow: hidden;
}

.mouse-cursor-gradient-tracking span {
  position: relative;
}

.mouse-cursor-gradient-tracking::before {
  --size: 0;
  content: '';
  position: absolute;
  left: var(--x);
  top: var(--y);
  width: var(--size);
  height: var(--size);
  background: radial-gradient(circle closest-side, pink, transparent);
  transform: translate(-50%, -50%);
  transition: width 0.2s ease, height 0.2s ease;
}

.mouse-cursor-gradient-tracking:hover::before {
  --size: 200px;
}

var btn = document.querySelector('.mouse-cursor-gradient-tracking')
btn.onmousemove = function(e) {
  var rect = e.target.getBoundingClientRect()
  var x = e.clientX - rect.left
  var y = e.clientY - rect.top
  btn.style.setProperty('--x', x + 'px')
  btn.style.setProperty('--y', y + 'px')
}

Explanation

--x and --y are used to track the position of the mouse on the button.
--size is used to keep modify of the gradient's dimensions.
background: radial-gradient(circle closest-side, pink, transparent); creates the gradient at the correct postion.

Browser support

96.5%

⚠️ Requires JavaScript.

https://caniuse.com/#feat=css-variables

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:not selector

The :not psuedo selector is useful for styling a group of elements, while leaving the last (or specified) element unstyled.

<ul class="css-not-selector-shortcut">
  <li>One</li>
  <li>Two</li>
  <li>Three</li>
  <li>Four</li>
</ul>

.css-not-selector-shortcut {
  display: flex;
}

ul {
  padding-left: 0;
}

li {
  list-style-type: none;
  margin: 0;
  padding: 0 0.75rem;
}

li:not(:last-child) {
  border-right: 2px solid #d2d5e4;
}

Explanation

li:not(:last-child) specifies that the styles should apply to all li elements except the :last-child.

Browser support

100.0%

https://caniuse.com/#feat=css-sel3

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Overflow scroll gradient

Adds a fading gradient to an overflowing element to better indicate there is more content to be scrolled.

<div class="overflow-scroll-gradient">
  <div class="overflow-scroll-gradient__scroller">
    Lorem ipsum dolor sit amet consectetur adipisicing elit. <br />
    Iure id exercitationem nulla qui repellat laborum vitae, <br />
    molestias tempora velit natus. Quas, assumenda nisi. <br />
    Quisquam enim qui iure, consequatur velit sit? <br />
    Lorem ipsum dolor sit amet consectetur adipisicing elit.<br />
    Iure id exercitationem nulla qui repellat laborum vitae, <br />
    molestias tempora velit natus. Quas, assumenda nisi. <br />
    Quisquam enim qui iure, consequatur velit sit?
  </div>
</div>

.overflow-scroll-gradient {
  position: relative;
}
.overflow-scroll-gradient::after {
  content: '';
  position: absolute;
  bottom: 0;
  width: 250px;
  height: 25px;
  background: linear-gradient(
    rgba(255, 255, 255, 0.001),
    white
  ); /* transparent keyword is broken in Safari */
  pointer-events: none;
}
.overflow-scroll-gradient__scroller {
  overflow-y: scroll;
  background: white;
  width: 240px;
  height: 200px;
  padding: 15px;
  line-height: 1.2;
}

Explanation

position: relative on the parent establishes a Cartesian positioning context for pseudo-elements.
::after defines a pseudo element.
background-image: linear-gradient(...) adds a linear gradient that fades from transparent to white (top to bottom).
position: absolute takes the pseudo element out of the flow of the document and positions it in relation to the parent.
width: 240px matches the size of the scrolling element (which is a child of the parent that has the pseudo element).
height: 25px is the height of the fading gradient pseudo-element, which should be kept relatively small.
bottom: 0 positions the pseudo-element at the bottom of the parent.
pointer-events: none specifies that the pseudo-element cannot be a target of mouse events, allowing text behind it to still be selectable/interactive.

Browser support

100.0%

https://caniuse.com/#feat=css-gradients

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Pretty text underline

A nicer alternative to text-decoration: underline or <u></u> where descenders do not clip the underline. Natively implemented as text-decoration-skip-ink: auto but it has less control over the underline.

<p class="pretty-text-underline">Pretty text underline without clipping descending letters.</p>

.pretty-text-underline {
  display: inline;
  text-shadow: 1px 1px #f5f6f9, -1px 1px #f5f6f9, -1px -1px #f5f6f9, 1px -1px #f5f6f9;
  background-image: linear-gradient(90deg, currentColor 100%, transparent 100%);
  background-position: bottom;
  background-repeat: no-repeat;
  background-size: 100% 1px;
}
.pretty-text-underline::-moz-selection {
  background-color: rgba(0, 150, 255, 0.3);
  text-shadow: none;
}
.pretty-text-underline::selection {
  background-color: rgba(0, 150, 255, 0.3);
  text-shadow: none;
}

Explanation

text-shadow uses 4 values with offsets that cover a 4x4 px area to ensure the underline has a "thick" shadow that covers the line where descenders clip it. Use a color that matches the background. For a larger font, use a larger px size. Additional values can create an even thicker shadow, and subpixel values can also be used.
background-image: linear-gradient(...) creates a 90deg gradient using the text color (currentColor).
The background-* properties size the gradient as 100% of the width of the block and 1px in height at the bottom and disables repetition, which creates a 1px underline beneath the text.
The ::selection pseudo selector rule ensures the text shadow does not interfere with text selection.

Browser support

100.0%

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Reset all styles

Resets all styles to default values with one property. This will not affect direction and unicode-bidi properties.

<div class="reset-all-styles">
  <h5>Title</h5>
  <p>
    Lorem ipsum dolor sit amet consectetur adipisicing elit. Iure id exercitationem nulla qui
    repellat laborum vitae, molestias tempora velit natus. Quas, assumenda nisi. Quisquam enim qui
    iure, consequatur velit sit?
  </p>
</div>

.reset-all-styles {
  all: initial;
}

Explanation

The all property allows you to reset all styles (inherited or not) to default values.

Browser support

95.8%

⚠️ MS Edge status is under consideration.

https://caniuse.com/#feat=css-all

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Shape separator

Uses an SVG shape to separate two different blocks to create more a interesting visual appearance compared to standard horizontal separation.

<div class="shape-separator"></div>

.shape-separator {
  position: relative;
  height: 48px;
  background: #333;
}
.shape-separator::after {
  content: '';
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 12'%3E%3Cpath d='m12 0l12 12h-24z' fill='%23fff'/%3E%3C/svg%3E");
  position: absolute;
  width: 100%;
  height: 12px;
  bottom: 0;
}

Explanation

position: relative on the element establishes a Cartesian positioning context for pseudo elements.
::after defines a pseudo element.
background-image: url(...) adds the SVG shape (a 24x12 triangle) as the background image of the pseudo element, which repeats by default. It must be the same color as the block that is being separated. For other shapes, we can use the URL-encoder for SVG.
position: absolute takes the pseudo element out of the flow of the document and positions it in relation to the parent.
width: 100% ensures the element stretches the entire width of its parent.
height: 12px is the same height as the shape.
bottom: 0 positions the pseudo element at the bottom of the parent.

Browser support

100.0%

https://caniuse.com/#feat=svg

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System font stack

Uses the native font of the operating system to get close to a native app feel.

<p class="system-font-stack">This text uses the system font.</p>

.system-font-stack {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen-Sans, Ubuntu,
    Cantarell, 'Helvetica Neue', Helvetica, Arial, sans-serif;
}

Explanation

The browser looks for each successive font, preferring the first one if possible, and falls back to the next if it cannot find the font (on the system or defined in CSS).

-apple-system is San Francisco, used on iOS and macOS (not Chrome however)
BlinkMacSystemFont is San Francisco, used on macOS Chrome
Segoe UI is used on Windows 10
Roboto is used on Android
Oxygen-Sans is used on Linux with KDE
Ubuntu is used on Ubuntu (all variants)
Cantarell is used on Linux with GNOME Shell
"Helvetica Neue" and Helvetica is used on macOS 10.10 and below (wrapped in quotes because it has a space)
Arial is a font widely supported by all operating systems
sans-serif is the fallback sans-serif font if none of the other fonts are supported

Browser support

100.0%

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Toggle switch

Creates a toggle switch with CSS only.

<input type="checkbox" id="toggle" class="offscreen" /> <label for="toggle" class="switch"></label>

.switch {
  position: relative;
  display: inline-block;
  width: 40px;
  height: 20px;
  background-color: rgba(0, 0, 0, 0.25);
  border-radius: 20px;
  transition: all 0.3s;
}

.switch::after {
  content: '';
  position: absolute;
  width: 18px;
  height: 18px;
  border-radius: 18px;
  background-color: white;
  top: 1px;
  left: 1px;
  transition: all 0.3s;
}

input[type='checkbox']:checked + .switch::after {
  transform: translateX(20px);
}

input[type='checkbox']:checked + .switch {
  background-color: #7983ff;
}

.offscreen {
  position: absolute;
  left: -9999px;
}

Explanation

This effect is styling only the <label> element to look like a toggle switch, and hiding the actual <input> checkbox by positioning it offscreen. When clicking the label associated with the <input> element, it sets the <input> checkbox into the :checked state.

The for attribute associates the <label> with the appropriate <input> checkbox element by its id.
.switch::after defines a pseudo-element for the <label> to create the circular knob.
input[type='checkbox']:checked + .switch::after targets the <label>'s pseudo-element's style when the checkbox is checked.
transform: translateX(20px) moves the pseudo-element (knob) 20px to the right when the checkbox is checked.
background-color: #7983ff; sets the background-color of the switch to a different color when the checkbox is checked.
.offscreen moves the <input> checkbox element, which does not comprise any part of the actual toggle switch, out of the flow of document and positions it far away from the view, but does not hide it so it is accessible via keyboard and screen readers.
transition: all 0.3s specifies all property changes will be transitioned over 0.3 seconds, therefore transitioning the <label>'s background-color and the pseudo-element's transform property when the checkbox is checked.

Browser support

100.0%

⚠️ Requires prefixes for full support.

https://caniuse.com/#feat=transforms2d

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Triangle

Creates a triangle shape with pure CSS.

<div class="triangle"></div>

.triangle {
  width: 0;
  height: 0;
  border-top: 20px solid #333;
  border-left: 20px solid transparent;
  border-right: 20px solid transparent;
}

Explanation

View this link for a detailed explanation.
The color of the border is the color of the triangle. The side the triangle tip points corresponds to the opposite border-* property. For example, a color on border-top means the arrow points downward.
Experiment with the px values to change the proportion of the triangle.

Browser support

100.0%

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Zebra striped list

Creates a striped list with alternating background colors, which is useful for differentiating siblings that have content spread across a wide row.

<ul>
  <li>Item 01</li>
  <li>Item 02</li>
  <li>Item 03</li>
  <li>Item 04</li>
  <li>Item 05</li>
</ul>

li:nth-child(odd) {
  background-color: #ddd;
}

Explanation

Use the :nth-child(odd) or :nth-child(even) pseudo-class to apply a different background color to elements that match based on their position in a group of siblings.
Note that you can use it to apply different styles to other HTML elements like div, tr, p, ol, etc.

Browser support

100.0%

https://caniuse.com/#feat=css-sel3

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src		src
static		static
.gitattributes		.gitattributes
.gitignore		.gitignore
.prettierignore		.prettierignore
.travis.yml		.travis.yml
CODE_OF_CONDUCT.md		CODE_OF_CONDUCT.md
CONTRIBUTING.md		CONTRIBUTING.md
LICENSE		LICENSE
README.md		README.md
_headers		_headers
advanced.svg		advanced.svg
config.js		config.js
gatsby-browser.js		gatsby-browser.js
gatsby-config.js		gatsby-config.js
gatsby-node.js		gatsby-node.js
gatsby-ssr.js		gatsby-ssr.js
netlify.toml		netlify.toml
package-lock.json		package-lock.json
package.json		package.json
snippet_template.md		snippet_template.md

License

islamCodehood/30-seconds-of-css

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30 Seconds of CSS

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Contributing

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Animation

Interactivity

Layout

Other

Visual

Animation

Bouncing loader

Explanation

Browser support

Button border animation

Explanation

Browser support

Donut spinner

Explanation

Browser support

Easing variables

Explanation

Browser support

Height transition

Explanation

Browser support

Hover shadow box animation

Explanation

Browser support

Hover underline animation

Explanation

Browser support

Interactivity

Disable selection

Explanation

Browser support

Popout menu

Explanation

Browser support

Sibling fade

Explanation

Browser support

Layout

Box-sizing reset

Explanation

Browser support

Clearfix

Note: This is only useful if you are still using float to build layouts. Please consider using a modern approach with flexbox layout or grid layout.

Explanation

Browser support

Constant width to height ratio

Explanation

Browser support

Display table centering

Explanation

Browser support

Evenly distributed children

Explanation

Browser support

Fit image in container

Explanation

Browser support

Flexbox centering

Explanation

Browser support

Ghost trick

Explanation

Browser support

Grid centering

Explanation

Browser support

Last item with remaining available height

Explanation

Browser support

Offscreen