Responsive Web Design Basics

How to create sites which respond to the needs and capabilities of the device they are viewed on.

Feb 12, 2019
• Updated May 14, 2020

The use of mobile devices to surf the web continues to grow at an astronomical pace, and these devices are often constrained by display size and require a different approach to how content is laid out on the screen.

Responsive web design, originally defined by Ethan Marcotte in A List Apart, responds to the needs of the users and the devices they’re using. The layout changes based on the size and capabilities of the device. For example, on a phone users would see content shown in a single column view; a tablet might show the same content in two columns.

A multitude of different screen sizes exist across phones, “phablets,” tablets, desktops, game consoles, TVs, and even wearables. Screen sizes are always changing, so it’s important that your site can adapt to any screen size, today or in the future. In addition, devices have different features with which we interact with them. For example some of your visitors will be using a touchscreen. Modern responsive design considers all of these things to optimize the experience for everyone.

Set the viewport

Pages optimized for a variety of devices must include a meta viewport tag in the head of the document.
A meta viewport tag gives the browser instructions on how to control the page’s dimensions and scaling.

To attempt to provide the best experience, mobile browsers render
the page at a desktop screen width (usually about 980px, though this varies
across devices), and then try to make the content look better by increasing
font sizes and scaling the content to fit the screen.
This means that font sizes may appear inconsistent to users,
who may have to double-tap or pinch-to-zoom
in order to see and interact with the content.

<!DOCTYPE html>
<html lang="en">
  <head>
    …
    <meta name="viewport" content="width=device-width, initial-scale=1">
    …
  </head>
  …

Using the meta viewport value width=device-width instructs the page to match
the screen’s width in device-independent pixels. A device (or density) independent pixel being a representation of a single pixel, which may on a high density screen consist of many physical pixels. This allows the page to reflow
content to match different screen sizes, whether rendered on a small mobile
phone or a large desktop monitor.

Screenshot of a page with the text hard to read as it is very zoomed out — An example of how the page loads in a device without the viewport meta tag. See this example on Glitch.

Screenshot of the same page with the text at a size that can be read — An example of how the page loads in a device with the viewport meta tag. See this example on Glitch.

Some browsers
keep the page’s width constant when rotating to landscape
mode, and zoom rather than reflow to fill the screen. Adding the value
initial-scale=1 instructs browsers to establish a 1:1 relationship between CSS
pixels and device-independent pixels regardless of device orientation, and
allows the page to take advantage of the full landscape width.

Caution:
To ensure that older browsers can properly parse the attributes,
use a comma to separate attributes.

The Does not have a <meta name="viewport"> tag with width or initial-scale
Lighthouse audit can help you automate the process of making sure that your HTML documents are using the viewport meta tag correctly.

Ensure an accessible viewport

In addition to setting an initial-scale,
you can also set the following attributes on the viewport:

minimum-scale
maximum-scale
user-scalable

When set, these can disable the user’s ability to zoom the viewport,
potentially causing accessibility issues.
Therefore we would not recommend using these attributes.

Size content to the viewport

On both desktop and mobile devices,
users are used to scrolling websites vertically but not horizontally;
forcing the user to scroll horizontally or to zoom out
in order to see the whole page results in a poor user experience.

When developing a mobile site with a meta viewport tag,
it’s easy to accidentally create page content that doesn’t quite fit within the specified viewport.
For example, an image that is displayed at a width wider than the viewport
can cause the viewport to scroll horizontally.
You should adjust this content to fit within the width of the viewport,
so that the user does not need to scroll horizontally.

The Content is not sized correctly for the viewport
Lighthouse audit can help you automate the process of detecting overflowing content.

Images

An image has fixed dimensions and if it is larger than the viewport will cause a scrollbar.
A common way to deal with this problem is to give all images a max-width of 100%.
This will cause the image to shrink to fit the space it has,
should the viewport size be smaller than the image.
However because the max-width, rather than the width is 100%,
the image will not stretch larger than its natural size.
It is generally safe to add the following to your stylesheet
so that you will never have a problem with images causing a scrollbar.

img {
max-width: 100%;
display: block;
}

Add the dimensions of the image to the img element

When using max-width: 100% you are overriding the natural dimensions of the image,
however you should still use the width and height attributes on your <img> tag.
This is because modern browsers will use this information to reserve space for the image
before it loads in,
this will help to avoid layout shifts as content loads.

Layout

Since screen dimensions and width in CSS pixels vary widely between devices
(for example, between phones and tablets, and even between different phones),
content should not rely on a particular viewport width to render well.

In the past, this required setting elements used to create layout in percentages.
In the example below, you can see a two-column layout with floated elements, sized using pixels.
Once the viewport becomes smaller than the total width of the columns, we have to scroll horizontally
to see the content.

Screenshot of a two-column layout with most of the second column outside the viewport — A floated layout using pixels. See this example on Glitch.

By using percentages for the widths, the columns always remain a certain percentage of the container.
This means that the columns become narrower, rather than creating a scrollbar.

Modern CSS layout techniques such as Flexbox, Grid Layout, and Multicol
make the creation of these flexible grids much easier.

Flexbox

This layout method is ideal when you have a set of items of different sizes
and you would like them to fit comfortably in a row or rows,
with smaller items taking less space and larger ones getting more space.

.items {
display: flex;
justify-content: space-between;
}

In a responsive design, you can use Flexbox to display items as a single row,
or wrapped onto multiple rows as the available space decreases.

CSS Grid Layout

CSS Grid Layout allows for the straightforward creation of flexible grids.
If we consider the earlier floated example,
rather than creating our columns with percentages,
we could use grid layout and the fr unit,
which represents a portion of the available space in the container.

.container {
display: grid;
grid-template-columns: 1fr 3fr;
}

Grid can also be used to create regular grid layouts,
with as many items as will fit.
The number of available tracks will be reduced as the screen size shrinks.
In the below demo, we have as many cards as will fit on each row,
with a minimum size of 200px.

Multiple-column Layout

For some types of layout you can use Multiple-column Layout (Multicol),
which can create responsive numbers of columns with the column-width property.
In the demo below, you can see that columns are added if there is room for another 200px column.

Media queries based on viewport size

Media queries enable us to create a responsive experience
where specific styles are applied to small screens, large screens, and anywhere in between.
The feature we are detecting here is therefore screen size,
and we can test for the following things.

width (min-width, max-width)
height (min-height, max-height)
orientation
aspect-ratio

All of these features have excellent browser support,
for more details including browser support information see
width,
height,
orientation, and
aspect-ratio on MDN.

The specification did include tests for device-width and device-height. These have been deprecated and should be avoided.
device-width and device-height tested for the actual size of the device window which was not useful in practice because
this may be different from the viewport the user is looking at,
for example if they have resized the browser window.

Media queries based on device capability

Given the range of devices available, we cannot make the assumption that every large device is a regular desktop
or laptop computer, or that people are only using a touchscreen on a small device.
With some newer additions to the media queries specification
we can test for features such as the type of pointer used to interact with the device
and whether the user can hover over elements.

hover
pointer
any-hover
any-pointer

Try viewing this demo on different devices,
such as a regular desktop computer and a phone or tablet.

These newer features have good support in all modern browsers. Find out more on the MDN pages for
hover,
any-hover,
pointer,
any-pointer.

Using `any-hover` and `any-pointer`

The features any-hover and any-pointer test if the user has the capability
to hover, or use that type of pointer even if it is not the primary way they are interacting with their device.
Be very careful when using these.
Forcing a user to switch to a mouse when they are using their touchscreen is not very friendly!
However, any-hover and any-pointer may be useful if it is important to work out what kind of device a user has.
For example, a laptop with a touchscreen and trackpad should match coarse and fine pointers,
in addition to the ability to hover.

How to choose breakpoints

Don’t define breakpoints based on device classes.
Defining breakpoints based on specific devices, products, brand names,
or operating systems that are in use today can result in a maintenance nightmare.
Instead, the content itself should determine how the layout adjusts to its container.

Pick major breakpoints by starting small, then working up

Design the content to fit on a small screen size first,
then expand the screen until a breakpoint becomes necessary.
This allows you to optimize breakpoints based on content
and maintain the least number of breakpoints possible.

Let’s work through the example we saw at the beginning: the weather forecast.
The first step is to make the forecast look good on a small screen.

Screenshot of a weather app at a mobile width — The app at a narrow width.

Next, resize the browser until there is too much white space between the elements,
and the forecast simply doesn’t look as good.
The decision is somewhat subjective, but above 600px is certainly too wide.

Screenshot of a weather app with wide gaps between items — The app at a point where we feel we should tweak the design.

To insert a breakpoint at 600px, create two media queries at the end of your CSS for the component,
one to use when the browser is 600px and below, and one for when it is wider than 600px.

@media (max-width: 600px) {}
@media (min-width: 601px) {
}

Finally, refactor the CSS. Inside the media query for a max-width of 600px,
add the CSS which is only for small screens. Inside the media query for a
min-width of 601px add CSS for larger screens.

Pick minor breakpoints when necessary

In addition to choosing major breakpoints when layout changes significantly,
it is also helpful to adjust for minor changes.
For example, between major breakpoints it may be helpful to adjust the margins or padding on an element,
or increase the font size to make it feel more natural in the layout.

Let’s start by optimizing the small screen layout.
In this case, let’s boost the font when the viewport width is greater than 360px.
Second, when there is enough space,
we can separate the high and low temperatures so that they’re on the same line
instead of on top of each other.
And let’s also make the weather icons a bit larger.

@media (min-width: 360px) {
body {
font-size: 1.0em;
}
}@media (min-width: 500px) {
.seven-day-fc .temp-low,
.seven-day-fc .temp-high {
display: inline-block;
width: 45%;
}
.seven-day-fc .seven-day-temp {
margin-left: 5%;
}
.seven-day-fc .icon {
width: 64px;
height: 64px;
}
}

Similarly, for the large screens it’s best to limit to maximum width of the forecast panel
so it doesn’t consume the whole screen width.

@media (min-width: 700px) {
.weather-forecast {
width: 700px;
}
}

Optimize text for reading

Classic readability theory suggests that an ideal column should contain 70 to 80 characters per line
(about 8 to 10 words in English).
Thus, each time the width of a text block grows past about 10 words,
consider adding a breakpoint.

Screenshot of a a page of text on a mobile device — The text as read on a mobile device.

Screenshot of a a page of text on a desktop browser — The text as read on a desktop browser with a breakpoint added to constrain the line length.

Let’s take a deeper look at the above blog post example.
On smaller screens, the Roboto font at 1em works perfectly giving 10 words per line,
but larger screens require a breakpoint.
In this case, if the browser width is greater than 575px, the ideal content width is 550px.

@media (min-width: 575px) {
article {
width: 550px;
margin-left: auto;
margin-right: auto;
}
}

Avoid simply hiding content

Be careful when choosing what content to hide or show depending on screen size.
Don’t simply hide content just because you can’t fit it on the screen.
Screen size is not a definitive indication of what a user may want.
For example, eliminating the pollen count from the weather forecast
could be a serious issue for spring-time allergy sufferers who need the information
to determine if they can go outside or not.

Once you’ve got your media query breakpoints set up,
you’ll want to see how your site looks with them.
You could resize your browser window to trigger the breakpoints,
but Chrome DevTools has a built-in feature that makes it easy to see how a page looks
under different breakpoints.