The Internet took off quicker than anyone would have
predicted, growing like crazy. Now, for the past few years, mobile
growth has exploded onto the scene. The growth of mobile Internet usage
is also far out pacing that of general Internet usage growth.
These days it is hard to find someone who doesn’t own a
mobile device, or multiple, connected to the Internet. In the UK there
are more mobile phones than people, and should trends continue mobile Internet usage will surpass that of desktop Internet usage within the year.
With the growth in mobile Internet usage comes the
question of how to build websites suitable for all users. The industry
response to this question has become responsive web design, also known
as RWD.
Responsive Overview
Responsive web design is the practice of building a
website suitable to work on every device and every screen size, no
matter how large or small, mobile or desktop. Responsive web design is
focused around providing an intuitive and gratifying experience for
everyone. Desktop computer and cell phone users alike all benefit from
responsive websites.
The responsive web design
term itself was coined, and largely developed, by Ethan Marcotte. A lot
of what is covered in this lesson was first talked about by Ethan
online and in his book Responsive Web Design, which is worth a read. Fig. 4Food Sense
has a beautiful website, responsive to all different viewport sizes. No
matter how large or small the viewport may be the Food Sense website
adjust, creating a natural user experience.
Responsive vs. Adaptive vs. Mobile
For some the term responsive may not be new, and others might be even more acquainted with the terms adaptive or mobile. Which may leave you wondering what exactly is the difference between all of them.
Responsive and adaptive web design are closely related,
and often transposed as one in the same. Responsive generally means to
react quickly and positively to any change, while adaptive means to be
easily modified for a new purpose or situation, such as change. With
responsive design websites continually and fluidly change based on
different factors, such as viewport width, while adaptive websites are
built to a groups of preset factors. A combination of the two is ideal,
providing the perfect formula for functional websites. Which term is
used specifically doesn’t make a huge difference.
Mobile, on the other hand, generally means to build a
separate website commonly on a new domain solely for mobile users. While
this does occasionally have it’s place, it normally isn’t a great idea.
Mobile websites can be extremely light but they do come with the
dependencies of a new code base and browser sniffing, all of which can
become an obstacle for both developers and users.
Currently the most popular technique lies within
responsive web design, favoring design that dynamically adapts to
different browser and device viewports, changing layout and content
along the way. This solution has the benefits of being all three,
responsive, adaptive, and mobile.
Flexible Layouts
Responsive web design is broken down into three main
components, including flexible layouts, media queries, and flexible
media. The first part, flexible layouts, is the practice of building the
layout of a website with a flexible grid, capable of dynamically
resizing to any width. Flexible grids are built using relative length
units, most commonly percentages or em units. These relative lengths are then used to declare common grid property values such as width, margin, or padding.
Relative Viewport Lengths
CSS3 introduced some new relative length units, specifically related to the viewport size of the browser or device. These new units include vw, vh, vmin, and vmax.
Overall support for these new units isn’t great, but it is growing. In
time they look to play a large roll in building responsive websites.
vw
Viewports width
vh
Viewports height
vmin
Minimum of the viewport’s height and width
vmax
Maximum of the viewport’s height and width
Flexible layouts do not advocate the use of fixed
measurement units, such as pixels or inches. Reason being, the viewport
height and width continually change from device to device. Website
layouts need to adapt to this change and fixed values have too many
constraints. Fortunately, Ethan pointed out an easy formula to help
identify the proportions of a flexible layout using relative values.
The formula is based around taking the target width of
an element and dividing it by the width of it’s parent element. The
result is the relative width of the target element.
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target ÷ context = result
Flexible Grid
Let’s see how this formula works inside of a two column layout. Below we have a parent division with the class of container wrapping both the section and aside elements. The goal is to have have the section on the left and the aside
on the right, with equal margins between the two. Normally the markup
and styles for this layout would look a bit like the following.
Using the flexible grid formula we can take all of the
fixed units of length and turn them into relative units. In this example
we’ll use percentages but em units would work equally as well. Notice, no matter how wide the parent container becomes, the section and aside margins and widths scale proportionally.
Taking the flexible layout concept, and formula, and
reapplying it to all parts of a grid will create a completely dynamic
website, scaling to every viewport size. For even more control within a
flexible layout, you can also leverage the min-width, max-width, min-height, and max-height properties.
The flexible layout approach alone isn’t enough. At
times the width of a browser viewport may be so small that even scaling
the the layout proportionally will create columns that are too small to
effectively display content. Specifically, when the layout gets too
small, or too large, text may become illegible and the layout may begin
to break. In this event, media queries can be used to help build a
better experience.
Media Queries
Media queries were built as an extension to media types
commonly found when targeting and including styles. Media queries
provide the ability to specify different styles for individual browser
and device circumstances, the width of the viewport or device
orientation for example. Being able to apply uniquely targeted styles opens up a world of opportunity and leverage to responsive web design.
Initializing Media Queries
There are a couple different ways to use media queries, using the @media rule inside of an existing style sheet, importing a new style sheet using the @import rule, or by linking to a separate style sheet from within the HTML document. Generally speaking it is recommend to use the @media rule inside of an existing style sheet to avoid any additional HTTP requests.
HTML
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<!-- Separate CSS File --><linkhref="styles.css"rel="stylesheet"media="all and (max-width: 1024px)">
Each media query may include a media type followed by one or more expressions. Common media types include all, screen, print, tv, and braille. The HTML5 specification includes new media types, even including 3d-glasses. Should a media type not be specified the media query will default the media type to screen.
The media query expression that follows the media type
may include different media features and values, which then allocate to
be true or false. When a media feature and value allocate to true, the
styles are applied. If the media feature and value allocate to false the
styles are ignored.
Logical Operators in Media Queries
Logical operators in media queries help build powerful
expressions. There are three different logical operators available for
use within media queries, including and, not, and only.
Using the and logical operator within a media query allows an extra condition to be added, making sure that a browser or devices does both a, b, c, and so forth. Multiple individual media queries can be comma separated, acting as an unspoken or operator. The example below selects all media types between 800 and 1024 pixels wide.
The not logical operator negates the
query, specifying any query but the one identified. In the example below
the expression applies to any device that does not have a color screen.
Black and white or monochrome screens would apply here for example.
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@medianotscreenand(color){...}
The only logical operator is a new
operator and is not recognized by user agents using the HTML4 algorithm,
thus hiding the styles from devices or browsers that don’t support
media queries. Below, the expression selects only screens in a portrait
orientation that have a user agent capable of rending media queries.
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@mediaonlyscreenand(orientation:portrait){...}
Omitting a Media Type
When using the not and only logical operators the media type may be left off. In this case the media type is defaulted to all.
Media Features in Media Queries
Knowing the media query syntax and how logical
operators work is a great introduction to media queries but the true
work comes with media features. Media features identify what attributes
or properties will be targeted within the media query expression.
Height & Width Media Features
One of the most common media features revolves around
determining a height or width for a device or browser viewport. The
height and width may be found by using the height, width, device-height, and device-width media features. Each of these media features may then also be prefixed with the min or max qualifiers, building a feature such as min-width or max-device-width.
The height and width features are based off the height and width of the viewport rendering area, the browser window for example. The device-height and device-width
features, on the other hand, are based off the height and width of the
output device, which may be larger than the actual rendering area.
Values for these height and width media features may be any length unit,
relative or absolute.
Within responsive design the most commonly used features include min-width and max-width. These help build responsive websites on desktops and mobile devices equally, avoiding any confusion with device features.
Using Minimum & Maximum Prefixes
The min and max prefixes can be used on quite a few media features. The min prefix indicates a values of greater than or equal to while the max prefix indicates a value of less than or equal to. Using min and max prefixes avoid any conflict with the general HTML syntax, specifically not using the < and > symbols.
Orientation Media Feature
The orientation media feature determines if a device is in the landscape or portrait orientation. The landscape mode is triggered when the display is wider than taller and the portrait mode is triggered when the display is taller than wider. This media feature plays a part largely with mobile devices.
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@mediaalland(orientation:landscape){...}
Aspect Ratio Media Features
The aspect-ratio and device-aspect-ratio features specifies the width/height pixel ratio of the targeted rendering area or output device. The min and max
prefixes are available to use with the different aspect ratio features,
identifying a ratio above or below that of which is stated.
The value for the aspect ratio feature consist of two
positive integers separated by a forward slash. The first integer
identifies the width in pixels while the second integer identifies the
height in pixels.
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@mediaalland(min-device-aspect-ratio:16/9){...}
Pixel Ratio Media Features
In addition to the aspect ratio media features there are also pixel-ratio media features. These features do include the device-pixel-ratio feature as well as min and max
prefixes. Specifically, the pixel ratio feature is great for
identifying high definition devices, including retina displays. Media
queries for doing so look like the following.
The resolution media feature specifies the resolution of the output device in pixel density, also known as dots per inch or DPI. The resolution media feature does accept the min and max prefixes. Additionally, the resolution media feature will accept dots per pixel (1.3dppx), dots per centimeter (118dpcm), and other length based resolution values.
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@mediaprintand(min-resolution:300dpi){...}
Other Media Features
Other media features include identifying available output colors with use of the color, color-index, and monochrome features, identifying bitmap devices with the grid feature, and identifying the scanning process of a television with the scan feature. These features are less common but equally as helpful when needed.
Media Query Browser Support
Unfortunately media queries do not work within
Internet Explorer 8 and below, as well as other legacy browsers. There
are, however, a couple suitable polyfills written in Javascript. Respond.js
is a lightweight polyfill that only looks for min/max-width media
types, which is perfect should those be the only media query types used.
CSS3-MediaQueries.js
is a more developed, and heavier, polyfill offering support for a
larger array of more complex media queries. Additionally, keep in mind
any polyfill can have performance concerns, and potentially slow down
websites. Make sure that any given polyfill is worth the performance
trade off.
Media Queries Demo
Using media queries we will now rewrite the flexible
layout we built previously. One of the current problems within the demo
appears when the aside width becomes uselessly small within smaller
viewports. Adding a media query for viewports under 420 pixels wide we can change the layout by turning off the floats and changing the widths of the section and aside.
Fig. 4
Without any media queries the section and aside become quite small. Perhaps too small to even contain any real content. Fig. 4
Using media queries to remove the floats and change their widths, the section and aside are now able to span the full width of the viewport, allowing breathing room for any existing content.
Identifying Breakpoints
Your instinct might be to write media query
breakpoints around common viewport sizes as determined by different
device resolutions, such as 320px, 480px, 768px, 1024px, 1224px, and so forth. This is a bad idea.
When building a responsive website it should adjust
to an array of different viewport sizes, regardless of the device.
Breakpoints should only be introduced when a website starts to break,
look weird, or the experience is being hampered.
Additionally, new devices and resolutions are being
released all of the time. Trying to keep up with these changes could be
an endless process.
Mobile First
One popular technique with using media queries is called mobile first. The mobile first
approach includes using styles targeted at smaller viewports as the
default styles for a website, then use media queries to add styles as
the viewport grows.
The operating belief behind mobile first design is that
a user on a mobile device, commonly using a smaller viewport, should’t
have to load the styles for a desktop computer only to have them over
written with mobile styles later. Doing so is a waste of bandwidth.
Bandwidth that is precious to any users looking for a snappy website.
The mobile first approach also advocates designing with
the constraints of a mobile user in mind. Before too long, the majority
of Internet consumption will be done on a mobile device. Plan for them
accordingly and develop intrinsic mobile experiences.
A breakout of mobile first media queries might look at bit like the following.
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/* Default styles first then media queries */@mediascreenand(min-width:400px){...}@mediascreenand(min-width:600px){...}@mediascreenand(min-width:1000px){...}@mediascreenand(min-width:1400px){...}
Additionally, downloading unnecessary media assets can
be stopped by using media queries. Generally speaking, avoiding CSS3
shadows, gradients, transforms, and animations within mobile styles
isn’t a bad idea either. When used excessively, they cause heavy loading
and can even reduce a device’s battery life.
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/* Default media */body{background:#ddd;}/* Media for larger devices */@mediascreenand(min-width:800px){body{background-image:url("bg.png")50%50%no-repeat;}}
Mobile First Demo
Adding media queries to our previous example, we
overwrote a handful of styles in order to have a better layout on
viewports under 420 pixels wide. Rewriting this code to use
the mobile styles first by default then adding media queries to adjust
for viewports over 420 pixels wide we build the following:
Notice, this is the same amount of code as before. The only exception here is that mobile devices only have to render only one
CSS declaration. All of the other styles are deferred, only loading on
larger viewports and done so without overwriting any initial styles.
Viewport
Mobile devices generally do a pretty decent job of
displaying websites these days. Sometimes they could use a little
assistance though, particularly around identifying the viewport size, scale, and resolution of a website. To remedy this, Apple invented the viewport meta tag. Fig. 4
Although this demo has media queries, many mobile
devices still do not know the initial width or scale of the website.
Therefore, they may not interrupt media queries.
Viewport Height & Width
Using the viewport meta tag with either the height or width
values will define the height or width of the viewport respectively.
Each value accepts either a positive integer or keyword. For the height property the keyword device-height value is accepted, and for the width property the keyword device-width is accepted. Using these keywords will inherit the device’s default height and width value.
For the best results, and the best looking website, it is recommend that you use the device defaults by applying the device-height and device-width values.
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<metaname="viewport"content="width=device-width">
Fig. 4
Letting devices know the intended width of the website, device-width in this case, allows the website to be sized properly and to pick up any qualifying media queries.
Viewport Scale
To control how a website is scaled on a mobile device, and how users can continue to scale a website, use the minimum-scale, maximum-scale, initial-scale, and user-scalable properties.
The initial-scale of a website should be set to 1
as this defines the ratio between the device height, while in a
portrait orientation, and the viewport size. Should a device be in
landscape mode this would be the ratio between the device width and the
viewport size. Values for initial-scale should always be a positive integer between 0 and 10.
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<metaname="viewport"content="initial-scale=2">
Fig. 4
Using an integer above 1 will zoom the website to be larger than the default scale. Generally speaking, this value will most commonly be set to 1.
The minimum-scale and maximum-scale values determine how small and how large a viewport may be scaled. When using minimum-scale the value should be a positive integer lower than or equal to the initial-scale. Using the same reasoning, the maximum-scale value should be a positive integer greater than or equal to the initial-scale. Values for both of these must also be between 0 and 10.
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<metaname="viewport"content="minimum-scale=0">
Generally speaking, these values should not be set to the same value as the initial-scale. This would disable any zooming, which can be accomplished instead by using the user-scalable value. Setting the user-scalable value to no will disable any zooming. Alternatively, setting the user-scalable value to yes will turn on zooming.
Turning off the ability to scale a website is a bad idea. It harms accessibility and usability, preventing those with disabilities from viewing a website as desired.
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<metaname="viewport"content="user-scalable=yes">
Viewport Resolution
Letting the browser decide how to scale a website based
off any viewport scale values usually does the trick. When more control
is needed, specifically over the resolution of a device, the target-densitydpi value may be used. The target-densitydpi viewport accepts a handful of values including device-dpi, high-dpi, medium-dpi, low-dpi, or an actual DPI number.
Using the target-densitydpi viewport value is rare, but extremely helpful when pixel by pixel control is needed.
The viewport meta tag will accept
individual values as well as multiple values, allowing multiple viewport
properties to be set at once. Setting multiple values requires comma
separating them within the content attribute value. One of the recommended viewport values is outlined below, using both the width and initial-scale properties.
Fig. 4
A combination of width=device-width and initial-scale=1 provide the initial size and zoom commonly required.
CSS Viewport Rule
Since the viewport meta tag revolves so
heavily around setting the styles of how a website should be rendered it
has been recommend to move the viewport from a meta tag with HTML to an
@ rule within CSS. This helps keep the style separated from content, providing a more semantic approach.
Currently some browsers have already implemented the @viewport rule, however support isn’t great across the board. The previously recommended viewport meta tag would look like the following @viewport rule in CSS.
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@viewport{width:device-width;zoom:1;}
Flexible Media
The final, equally important aspect to responsive web
design involves flexible media. As viewports begin to change size media
doesn’t always follow suit. Images, videos, and other media types need
to be scalable, changing their size as the size of the viewport changes.
One quick way to make media scalable is by using the max-width property with a value of 100%. Doing so ensures that as the viewport gets smaller any media will scale down according to its containers width.
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img,video,canvas{max-width:100%;}
Flexible Media Demo
Flexible Embedded Media
Unfortunately the max-width property doesn’t work well for all instances of media, specifically around iframes
and embedded media. When it comes to third party websites, such as
YouTube, who use iframes for embedded media this is a huge
disappointment. Fortunately, there is a work around.
To get embedded media to be fully responsive, the
embedded element needs to be absolutely positioned within a parent
element. The parent element needs to have a width of 100% so that it may scale based on the width of the viewport. The parent element also needs to have a height of 0 to trigger the hasLayout mechanism within Internet Explorer.
Padding is then given to the bottom of the parent
element, the value of which is set in the same aspect ratio of the
video. This allows the height of the parent element to be proportionate
to that of it’s width. Remember the responsive design formula from
before? If a video has an aspect ratio of 16:9, 9 divided by 16 equals .5625, thus requiring a bottom padding of 56.25%.
Padding on the bottom and not the top is specifically used to prevent
Internet Explorer 5.5 from breaking, and treating the parent element as
an absolutely positioned element.
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