Most modern websites use responsive web design techniques to ensure they look good, are readable, and remain usable on devices with any screen size, i.e. mobile phones, tablets, laptops, desktop PC monitors, televisions, projectors, and more.

Sites using these techniques have a single template, which modifies the layout in response to the screen dimensions:

  • Smaller screens typically show a linear, single-column view where UI controls such as menus are activated by clicking (hamburger) icons.
  • Larger screens show more information, perhaps with horizontally-aligned sidebars. UI controls such as menu items may always be visible for easier access.

One big part of responsive web design is the implementation of a CSS or JavaScript media query to detect device size and automatically serve up the appropriate design for that size. We’re going to discuss why these queries are important and how to work with them, but first, let’s discuss responsive design in general.

Why Is Responsive Design Important?

It’s impossible to provide a single page layout and expect it to work everywhere.

When mobile phones first gained rudimentary web access in the early 2000s, site owners would often create two or three separate page templates loosely based around mobile and desktop views. That became increasingly impractical as the variety of devices grew exponentially.

Today, there are numerous screen sizes ranging from tiny wristwatch displays to huge 8 K monitors and beyond. Even if you only consider mobile phones, recent devices can have a higher resolution than many low-end laptops.

Mobile usage has also grown beyond that of desktop computers. Unless your site has a specific set of users, you can expect the majority of people to access it from a smartphone. Small-screen devices are no longer an afterthought and should be considered from the start, despite most web designers, developers, and clients continuing to use a standard PC.

Google has recognized the importance of mobile devices. Sites rank better in Google search when they’re usable and perform well on a smartphone. Good content remains vital, but a slow-loading site that fails to adapt to the screen dimensions of your userbase could harm your business.

Finally, consider accessibility. A site that works for everyone, no matter what device they’re using, will reach a larger audience. Accessibility is a legal requirement in many countries, but even if it’s not where you are, consider that more viewers will lead to more conversions and higher profitability.

body a.novashare-ctt{display:block;background:#00abf0;margin:30px auto;padding:20px 20px 20px 15px;color:#fff;text-decoration:none!important;box-shadow:none!important;-webkit-box-shadow:none!important;-moz-box-shadow:none!important;border:none;border-left:5px solid #00abf0}body a.novashare-ctt:hover{color:#fff;border-left:5px solid #008cc4}body a.novashare-ctt:visited{color:#fff}body a.novashare-ctt *{pointer-events:none}body a.novashare-ctt .novashare-ctt-tweet{display:block;font-size:18px;line-height:27px;margin-bottom:10px}body a.novashare-ctt .novashare-ctt-cta-container{display:block;overflow:hidden}body a.novashare-ctt .novashare-ctt-cta{float:right}body a.novashare-ctt.novashare-ctt-cta-left .novashare-ctt-cta{float:left}body a.novashare-ctt .novashare-ctt-cta-text{font-size:16px;line-height:16px;vertical-align:middle}body a.novashare-ctt .novashare-ctt-cta-icon{margin-left:10px;display:inline-block;vertical-align:middle}body a.novashare-ctt .novashare-ctt-cta-icon svg{vertical-align:middle;height:18px}body a.novashare-ctt.novashare-ctt-simple{background:0 0;padding:10px 0 10px 20px;color:inherit}body a.novashare-ctt.novashare-ctt-simple-alt{background:#f9f9f9;padding:20px;color:#404040}body a.novashare-ctt.novashare-ctt-simple-alt:hover,body a.novashare-ctt.novashare-ctt-simple:hover{border-left:5px solid #008cc4}body a.novashare-ctt.novashare-ctt-simple .novashare-ctt-cta,body a.novashare-ctt.novashare-ctt-simple-alt .novashare-ctt-cta{color:#00abf0}body a.novashare-ctt.novashare-ctt-simple-alt:hover .novashare-ctt-cta,body a.novashare-ctt.novashare-ctt-simple:hover .novashare-ctt-cta{color:#008cc4}In order to tackle responsive web design, you first need to understand JavaScript media queries 🤓 Let’s dive in! 🚀Click to Tweet

How Does Responsive Design Work?

The basis of responsive design is media queries: a CSS technology that can apply styles according to metrics such as the output type (screen, printer, or even speech), screen dimensions, display aspect ratio, device orientation, color depth, and pointer accuracy. Media queries can also take user preferences into account, including reduced animations, light/dark mode, and higher contrast.

The examples we’ve shown demonstrate media queries using screen width only, but sites can be considerably more flexible. Refer to the full set of options on MDN for details.

Media query support is excellent and has been in browsers for more than a decade. Only IE8 and below have no support. They ignore styles applied by media queries, but this can sometimes be a benefit (read more in the Best Practices section below).

There are three standard ways to apply styles using media queries. The first loads specific stylesheets in HTML code. For example, the following tag loads the wide.css stylesheet when a device has a screen that is at least 800 pixels wide:

Secondly, stylesheets can be conditionally loaded in CSS files using an @import at-rule:

/* main.css */
@import url('wide.css') screen and (min-width: 800px);


Note that @import should be avoided because each imported CSS file is render-blocking. HTML tags are downloaded in parallel, whereas @import downloads files in series.

More typically, you’ll apply media queries in stylesheets using a @media CSS at-rule block that modifies specific styles. For example:

/* default styles */
main {
  width: 400px;

/* styles applied when screen has a width of at least 800px */
@media screen and (min-width: 800px) {
  main {
    width: 760px;

Developers can apply whichever media query rules are necessary to adapt the layout of a site.

Media Query Best Practises

When media queries were first devised, many sites opted for a set of rigidly fixed layouts. This is conceptually easier to design and code because it effectively replicates a limited set of page templates. For example:

  1. Screen widths less than 600px use a 400px-wide mobile-like layout.
  2. Screen widths between 600px and 999px use a 600px-wide tablet-like layout.
  3. Screen widths greater than 1,000px use a 1000px-wide desktop-like layout.

The technique is flawed. The results on very small and very large screens can look poor, and CSS maintenance can be required as devices and screen sizes change over time.

A better option is to use a mobile-first fluid design with breakpoints that adapt the layout at certain sizes. In essence, the default layout uses the simplest small-screen styles that position elements in linear vertical blocks.

For example,