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`all` Property

A property for defining the reset of all properties of an element

a {
  all: initial;
}

Use with a

PostCSS Plugin

Break Properties

Properties for defining the break behavior between and within boxes

Specification

a {
  break-inside: avoid;
  break-before: avoid-column;
  break-after: always;
}

Use with a

PostCSS Plugin

Custom Properties

A syntax for defining custom values accepted by all CSS properties

Specification

img {
  --some-length: 32px;

  height: var(--some-length);
  width: var(--some-length);
}

Use with a

PostCSS Plugin

`font-variant` Property

A property for defining the usage of alternate glyphs in a font

Specification

h2 {
  font-variant: small-caps;
}

Use with a

PostCSS Plugin

Gap Properties

Properties for defining gutters within a layout

Specification

.grid-1 {
  gap: 20px;
}

.grid-2 {
  column-gap: 40px;
  row-gap: 20px;
}

Use with a

PostCSS Plugin

Grid Layout

A syntax for using a grid concept to lay out content

Specification

section {
  display: grid;
  grid-template-columns: 100px 100px 100px;
  grid-gap: 10px;
}

Use with a

PostCSS Plugin

Media Query Ranges

A syntax for defining media query ranges using ordinary comparison operators

Specification

@media (width < 480px) {}

@media (480px <= width < 768px) {}

@media (width >= 768px) {}

Use with a

PostCSS Plugin

`:any-link` Hyperlink Pseudo-Class

A pseudo-class for matching anchor elements independent of whether they have been visited

Specification

nav :any-link > span {
  background-color: yellow;
}

Use with a

PostCSS Plugin

Case-Insensitive Attributes

An attribute selector matching attribute values case-insensitively

Specification

[frame=hsides i] {
  border-style: solid none;
}

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PostCSS Plugin

`color-adjust` Property

The color-adjust property is a non-standard CSS extension that can be used to force printing of background colors and images

Specification

.background {
  background-color:#ccc;
}
.background.color-adjust {
  color-adjust: economy;
}
.background.color-adjust-exact {
  color-adjust: exact;
}

`:dir` Directionality Pseudo-Class

A pseudo-class for matching elements based on their directionality

Specification

blockquote:dir(rtl) {
  margin-right: 10px;
}

blockquote:dir(ltr) {
  margin-left: 10px;
}

Use with a

PostCSS Plugin

Double Position Gradients

A syntax for using two positions in a gradient.

Specification

.pie_chart {
  background-image: conic-gradient(yellowgreen 40%, gold 0deg 75%, #f06 0deg);
}

Use with a

PostCSS Plugin

`:focus-visible` Focus-Indicated Pseudo-Class

A pseudo-class for matching focused elements that indicate that focus to a user

Specification

:focus:not(:focus-visible) {
  outline: 0;
}

Use with a

`:focus-within` Focus Container Pseudo-Class

A pseudo-class for matching elements that are either focused or that have focused descendants

Specification

form:focus-within {
  background: rgba(0, 0, 0, 0.3);
}

Use with a

`gray()` Function

A function for specifying fully desaturated colors

Specification

p {
  color: gray(50);
}

Use with a

PostCSS Plugin

`:has()` Relational Pseudo-Class

A pseudo-class for matching ancestor and sibling elements

Specification

a:has(> img) {
  display: block;
}

Use with a

Hexadecimal Alpha Notation

A 4 & 8 character hex color notation for specifying the opacity level

Specification

section {
  background-color: #f3f3f3f3;
  color: #0003;
}

Use with a

PostCSS Plugin

`hwb()` Function

A function for specifying colors by hue and then a degree of whiteness and blackness to mix into it

Specification

p {
  color: hwb(120 44% 50%);
}

Use with a

PostCSS Plugin

`image-set()` Function

A function for specifying image sources based on the user’s resolution

Specification

p {
  background-image: image-set(
    "foo.png" 1x,
    "foo-2x.png" 2x,
    "foo-print.png" 600dpi
  );
}

Use with a

PostCSS Plugin

`:in-range` and `:out-of-range` Pseudo-Classes

A pseudo-class for matching elements that have range limitations

Specification

input:in-range {
  background-color: rgba(0, 255, 0, 0.25);
}
input:out-of-range {
  background-color: rgba(255, 0, 0, 0.25);
  border: 2px solid red;
}

`lab()` Function

A function for specifying colors expressed in the CIE Lab color space

Specification

body {
  color: lab(240 50 20);
}

Use with a

PostCSS Plugin

`lch()` Function

A function for specifying colors expressed in the CIE Lab color space with chroma and hue

Specification

body {
  color: lch(53 105 40);
}

Use with a

PostCSS Plugin

Logical Properties and Values

Flow-relative (left-to-right or right-to-left) properties and values

Specification

span:first-child {
  float: inline-start;
  margin-inline-start: 10px;
}

Use with a

PostCSS Plugin

`:matches()` Matches-Any Pseudo-Class

A pseudo-class for matching elements in a selector list

Specification

p:matches(:first-child, .special) {
  margin-top: 1em;
}

Use with a

PostCSS Plugin

`:not()` Negation List Pseudo-Class

A pseudo-class for ignoring elements in a selector list

Specification

p:not(:first-child, .special) {
  margin-top: 1em;
}

Use with a

PostCSS Plugin

`overflow` Shorthand Property

A property for defining overflow-x and overflow-y

Specification

html {
  overflow: hidden auto;
}

Use with a

PostCSS Plugin

`overflow-wrap` Property

A property for defining whether to insert line breaks within words to prevent overflowing

Specification

p {
  overflow-wrap: break-word;
}

Use with a

PostCSS Plugin

Place Properties

Properties for defining alignment within a layout

Specification

.example {
  place-content: flex-end;
  place-items: center / space-between;
  place-self: flex-start / center;
}

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PostCSS Plugin

`:read-only` and `:read-write` selectors

Pseudo-classes to match elements which are considered user-alterable

Specification

input:read-only {
  background-color: #ccc;
}

`rebeccapurple` Color

A particularly lovely shade of purple in memory of Rebecca Alison Meyer

Specification

html {
  color: rebeccapurple;
}

Use with a

PostCSS Plugin

`system-ui` Font Family

A generic font used to match the user’s interface

Specification

body {
  font-family: system-ui;
}

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PostCSS Plugin

`:blank` Empty-Value Pseudo-Class

A pseudo-class for matching form elements when they are empty

Specification

input:blank {
  background-color: yellow;
}

Use with a

Color Functional Notation

A space and slash separated notation for specifying colors

Specification

em {
  background-color: hsl(120deg 100% 25%);
  box-shadow: 0 0 0 10px hwb(120deg 100% 25% / 80%);
  color: rgb(0 255 0);
}

Use with a

PostCSS Plugin

Custom Media Queries

An at-rule for defining aliases that represent media queries

Specification

@custom-media --narrow-window (max-width: 30em);

@media (--narrow-window) {}

Use with a

PostCSS Plugin

Custom Selectors

An at-rule for defining aliases that represent selectors

Specification

@custom-selector :--heading h1, h2, h3, h4, h5, h6;

article :--heading + p {}

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PostCSS Plugin

Nesting Rules

A syntax for nesting relative rules within rules

Specification

article {
  & p {
    color: #333;
  }
}

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PostCSS Plugin

`overscroll-behavior` Property

Properties for controlling when the scroll position of a scroll container reaches the edge of a scrollport

Specification

.messages {
  height: 220px;
  overflow: auto;
  overscroll-behavior-y: contain;
}

body {
  margin: 0;
  overscroll-behavior: none;
}

`prefers-color-scheme` Media Query

A media query to detect if the user has requested the system use a light or dark color theme

Specification

body {
  background-color: white;
  color: black;
}

@media (prefers-color-scheme: dark) {
  body {
    background-color: black;
    color: white;
  }
}

Use with a

`prefers-reduced-motion` Media Query

A media query to detect if the user has requested less animation and general motion on the page

Specification

.animation {
  animation: vibrate 0.3s linear infinite both; 
}

@media (prefers-reduced-motion: reduce) {
  .animation {
    animation: none;
  }
}

`:where()` Zero-Specificity Pseudo-Class

A pseudo-class for matching elements in a selector list without contributing specificity

Specification

a:where(:not(:hover)) {
  text-decoration: none;
}

Custom Environment Variables

A syntax for using custom values accepted by CSS globally

Specification

@media (max-width: env(--brand-small)) {
  body {
    padding: env(--brand-spacing);
  }
}

Use with a

PostCSS Plugin

When/Else Rules

At-rules for specifying media queries and support queries in a single grammar

Specification

@when media(width >= 640px) and (supports(display: flex) or supports(display: grid)) {
  /* A */
} @else media(pointer: coarse) {
  /* B */
} @else {
  /* C */
}