CSS Protips 
A collection of tips to help take your CSS skills pro.
[!TIP]
For other great lists check out @sindresorhus's curated list of awesome lists.
Contents
Protips
- Use a CSS Reset
- Inherit
box-sizing
- Use
unset Instead of Resetting All Properties
- Use
:not() to Apply/Unapply Borders on Navigation
- Check if Font Is Installed Locally
- Add
line-height to body
- Set
:focus for Form Elements
- Vertically-Center Anything
- Use
aspect-ratio Instead of Height/Width
- Comma-Separated Lists
- Select Items Using Negative
nth-child
- Use SVG for Icons
- Use the "Lobotomized Owl" Selector
- Use
max-height for Pure CSS Sliders
- Equal-Width Table Cells
- Get Rid of Margin Hacks With Flexbox
- Use Attribute Selectors with Empty Links
- Control Specificity Better With
:is()
- Style "Default" Links
- Intrinsic Ratio Boxes
- Style Broken Images
- Use
rem for Global Sizing; Use em for Local Sizing
- Hide Autoplay Videos That Aren't Muted
- Use
:root for Flexible Type
- Set
font-size on Form Elements for a Better Mobile Experience
- Use Pointer Events to Control Mouse Events
- Set
display: none on Line Breaks Used as Spacing
- Use
:empty to Hide Empty HTML Elements
- Use
margin-inline instead of margin
Use a CSS Reset
CSS resets help enforce style consistency across different browsers with a clean slate for styling elements. There are plenty of reset patterns to find, or you can use a more simplified reset approach:
*,
*::before,
*::after {
box-sizing: border-box;
margin: 0;
padding: 0;
}
Now elements will be stripped of margins and padding, and box-sizing lets you manage layouts with the CSS box model.
[!TIP]
If you follow the Inherit box-sizing tip below you might opt to not include the box-sizing property in your CSS reset.
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Inherit box-sizing
Let box-sizing be inherited from html:
html {
box-sizing: border-box;
}
*,
*::before,
*::after {
box-sizing: inherit;
}
This makes it easier to change box-sizing in plugins or other components that leverage other behavior.
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Use unset Instead of Resetting All Properties
When resetting an element's properties, it's not necessary to reset each individual property:
button {
background: none;
border: none;
color: inherit;
font: inherit;
outline: none;
padding: 0;
}
You can specify all of an element's properties using the all shorthand. Setting the value to unset changes an element's properties to their initial values:
button {
all: unset;
}
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Use :not() to Apply/Unapply Borders on Navigation
Instead of putting on the border...
/* add border */
.nav li {
border-right: 1px solid #666;
}
...and then taking it off the last element...
/* remove border */
.nav li:last-child {
border-right: none;
}
...use the :not() pseudo-class to only apply to the elements you want:
.nav li:not(:last-child) {
border-right: 1px solid #666;
}
Here, the CSS selector is read as a human would describe it.
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Check if Font Is Installed Locally
You can check if a font is installed locally before fetching it remotely, which is a good performance tip, too.
@font-face {
font-family: "Dank Mono";
src:
/* Full name */
local("Dank Mono"),
/* Postscript name */ local("Dank Mono"),
/* Otherwise, download it! */ url("//...a.server/fonts/DankMono.woff");
}
code {
font-family: "Dank Mono", system-ui-monospace;
}
H/T to Adam Argyle for sharing this protip and demo.
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Add line-height to body
You don't need to add line-height to each <p>, <h*>, et al. separately. Instead, add it to body:
body {
line-height: 1.5;
}
This way textual elements can inherit from body easily.
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Sighted keyboard users rely on focus to determine where keyboard events go in the page. Make focus for form elements stand out and consistent than a browser's default implementation:
a:focus,
button:focus,
input:focus,
select:focus,
textarea:focus {
box-shadow: none;
outline: #000 dotted 2px;
outline-offset: 0.05em;
}
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Vertically-Center Anything
No, it's not black magic, you really can center elements vertically. You can do this with flexbox...
html,
body {
height: 100%;
}
body {
align-items: center;
display: flex;
justify-content: center;
}
...and also with CSS Grid:
body {
display: grid;
height: 100vh;
place-items: center;
}
[!TIP]
Want to center something else? Vertically, horizontally...anything, anytime, anywhere? CSS-Tricks has a nice write-up on doing all of that.
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Use aspect-ratio Instead of Height/Width
The aspect-ratio property allows you to easily size elements and maintain consistent width-to-height ratio. This is incredibly useful in responsive web design to prevent layout shift. Use object-fit with it to prevent disrupting the layout if the height/width values of images changes.
img {
aspect-ratio: 16 / 9; /* width / height */
object-fit: cover;
}
Learn more about the aspect-ratio property in this web.dev post.
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Comma-Separated Lists
Make list items look like a real, comma-separated list:
ul > li:not(:last-child)::after {
content: ",";
}
Use the :not() pseudo-class and no comma will be added to the last item.
[!NOTE]
This tip may not be ideal for accessibility, specifically screen readers. And copy/paste from the browser doesn't work with CSS-generated content. Proceed with caution.
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Select Items Using Negative nth-child
Use negative nth-child in CSS to select items 1 through n.
li {
display: none;
}
/* select items 1 through 3 and display them */
li:nth-child(-n + 3) {
display: block;
}
Or, since you've already learned a little about using :not(), try:
/* select all items except the first 3 and display them */
li:not(:nth-child(-n + 3)) {
display: block;
}
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Use SVG for Icons
There's no reason not to use SVG for icons:
.logo {
background: url("logo.svg");
}
SVG scales well for all resolution types and is supported in all browsers back to IE9. Ditch your .png, .jpg, or .gif-jif-whatev files.
[!NOTE]
If you have SVG icon-only buttons for sighted users and the SVG fails to load, this will help maintain accessibility:
.no-svg .icon-only::after {
content: attr(aria-label);
}
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Use the "Lobotomized Owl" Selector
It may have a strange name but using the universal selector (*) with the adjacent sibling selector (+) can provide a powerful CSS capability:
* + * {
margin-top: 1.5em;
}
In this example, all elements in the flow of the document that follow other elements will receive margin-top: 1.5em.
[!TIP]
For more on the "lobotomized owl" selector, read Heydon Pickering's post on A List Apart.
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Use max-height for Pure CSS Sliders
Implement CSS-only sliders using max-height with overflow hidden:
.slider {
max-height: 200px;
overflow-y: hidden;
width: 300px;
}
.slider:hover {
max-height: 600px;
overflow-y: scroll;
}
The element expands to the max-height value on hover and the slider displays as a result of the overflow.
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Equal-Width Table Cells
Tables can be a pain to work with. Try using table-layout: fixed to keep cells at equal width:
.calendar {
table-layout: fixed;
}
Pain-free table layouts.
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Get Rid of Margin Hacks With Flexbox
When working with column gutters you can get rid of nth-, first-, and last-child hacks by using flexbox's space-between property:
.list {
display: flex;
justify-content: space-between;
}
.list .person {
flex-basis: 23%;
}
Now column gutters always appear evenly-spaced.
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Use Attribute Selectors with Empty Links
Display links when the <a> element has no text value but the href attribute has a link:
a[href^="http"]:empty::before {
content: attr(href);
}
That's really convenient.
[!NOTE]
This tip may not be ideal for accessibility, specifically screen readers. And copy/paste from the browser doesn't work with CSS-generated content. Proceed with caution.
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Control Specificity Better with :is()
The :is() pseudo-class is used to target multiple selectors at once, reducing redundancy and enhancing code readability. This is incredibly useful for writing large selectors in a more compact form.
:is(section, article, aside, nav) :is(h1, h2, h3, h4, h5, h6) {
color: green;
}
The above ruleset is equivalent to the following number selector rules...
section h1,
section h2,
section h3,
section h4,
section h5,
section h6,
article h1,
article h2,
article h3,
article h4,
article h5,
article h6,
aside h1,
aside h2,
aside h3,
aside h4,
aside h5,
aside h6,
nav h1,
nav h2,
nav h3,
nav h4,
nav h5,
nav h6 {
color: green;
}
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Style "Default" Links
Add a style for "default" links:
a[href]:not([class]) {
color: #008000;
text-decoration: underline;
}
Now links that are inserted via a CMS, which don't usually have a class attribute, will have a distinction without generically affecting the cascade.
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Intrinsic Ratio Boxes
To create a box with an intrinsic ratio, all you need to do is apply top or bottom padding to a div:
.container {
height: 0;
padding-bottom: 20%;
position: relative;
}
.container div {
border: 2px dashed #ddd;
height: 100%;
left: 0;
position: absolute;
top: 0;
width: 100%;
}
Using 20% for padding makes the height of the box equal to 20% of its width. No matter the width of the viewport, the child div will keep its aspect ratio (100% / 20% = 5:1).
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Style Broken Images
Make broken images more aesthetically-pleasing with a little bit of CSS:
img {
display: block;
font-family: sans-serif;
font-weight: 300;
height: auto;
line-height: 2;
position: relative;
text-align: center;
width: 100%;
}
Now add pseudo-elements rules to display a user message and URL reference of the broken image:
img::before {
content: "We're sorry, the image below is broken :(";
display: block;
margin-bottom: 10px;
}
img::after {
content: "(url: " attr(src) ")";
display: block;
font-size: 12px;
}
[!TIP]
Learn more about styling for this pattern in Ire Aderinokun's post.
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Use rem for Global Sizing; Use em for Local Sizing
After setting the base font size at the root (html { font-size: 100%; }), set the font size for textual elements to em:
h2 {
font-size: 2em;
}
p {
font-size: 1em;
}
Then set the font-size for modules to rem:
article {
font-size: 1.25rem;
}
aside .module {
font-size: 0.9rem;
}
Now each module becomes compartmentalized and easier to style, more maintainable, and flexible.
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Hide Autoplay Videos That Aren't Muted
This is a great trick for a custom user stylesheet. Avoid overloading a user with sound from a video that autoplays when the page is loaded. If the sound isn't muted, don't show the video:
video[autoplay]:not([muted]) {
display: none;
}
Once again, we're taking advantage of using the :not() pseudo-class.
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Use :root for Flexible Type
The type font size in a responsive layout should be able to adjust with each viewport. You can calculate the font size based on the viewport height and width using :root:
:root {
font-size: calc(1vw + 1vh + 0.5vmin);
}
Now you can utilize the root em unit based on the value calculated by :root:
body {
font: 1rem/1.6 sans-serif;
}
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To avoid mobile browsers (iOS Safari, et al.) from zooming in on HTML form elements when a <select> drop-down is tapped, add font-size to the selector rule:
input[type="text"],
input[type="number"],
select,
textarea {
font-size: 16px;
}
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Use Pointer Events to Control Mouse Events
Pointer events allow you to specify how the mouse interacts with the element it's touching. To disable the default pointer event on a button, for instance:
button:disabled {
opacity: 0.5;
pointer-events: none;
}
It's that simple.
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Set display: none on Line Breaks Used as Spacing
As Harry Roberts pointed out, this can help prevent CMS users from using extra line breaks for spacing:
br + br {
display: none;
}
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Use :empty to Hide Empty HTML Elements
If you have HTML elements that are empty, i.e., the content has yet to be set either by a CMS or dynamically injected (e.g., <p class="error-message"></p>) and it's creating unwanted space on your layout, use the :empty pseudo-class to hide the element on the layout.
:empty {
display: none;
}
[!NOTE]
Keep in mind that elements with whitespace aren't considered empty, e.g., <p class="error-message"> </p>.
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Support
Current versions of Chrome, Firefox, Safari, and Edge.
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Use margin-inline instead of margin
margin-inline defines the inline start and end margins of an element. So instead of using margin-left and margin-right we can use the inline property to define both.
.div {
margin-inline: auto;
}
The same can be done for margin-block with defines the block start and end margins, i.e., margin-top and margin-bottom.
.div {
margin-block: auto;
}
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Translations
[!NOTE]
I've had less time available to maintain the growing list of translated tips; adding a new tip requires including it with over a dozen translations. For that reason, translated README files are likely to not include all the tips listed on the main README file.
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一份精选的 CSS 技巧合集，帮助开发者提升 CSS 技能，内容涵盖重置样式、flexbox、选择器以及兼顾无障碍的写法等。