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Are We Ready to Use Flexbox?

By Nick Salloum



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flexible adjective
1. capable of bending or being bent, able to be easily modified to respond to altered circumstances or conditions.

box noun
1. a rigid typically rectangular container.

The Flexible Box Module, a.k.a. flexbox, is all the latest and greatest at the moment. It digs into the fundamentals of the CSS box-model, providing us with a powerful and highly useful module for layout configurations. It is easily defined in our CSS and markup, and responsive adaptations are just a media query away. Think about a world where we don’t have to clear floats or utilise frameworks or masses of code to create responsive grids. Flexbox does all the dirty work. For us, it’s just a simple implementation. We define a flex container, and in it we have flex items.

flexbox example

Exactly What is Flexbox?

Here’s a definition of flexbox, according to MDN:

The CSS3 Flexible Box, or flexbox, is a layout mode providing for the arrangement of elements on a page such that the elements behave predictably when the page layout must accommodate different screen sizes and different display devices.

In simple words, we can mark up a few flex items inside a flex container, and define the layout arrangement with our CSS. We have numerous options when defining our layout arrangement that make possibilities endless. Here are a few:

  1. flex-direction – With this property we can specify if we want the items to be in a row or column, and also if we want the items to be in order of markup appearance or reversed.
  2. justify-content – Let’s us declare how the browser should distribute the available space between elements. In other words, if we have 3 elements at a combined total width of 50% of their container, we can specify whether to pack the elements to the left, right, center, distribute from left to right with an even amount of spacing in between them, along with some other options.
  3. flex-wrap – With this property, we can specify whether we want our flex items to jump to a new line if the flex container runs out of space.

The points above are just a small sampling of the capabilities of flexbox, and you can get much further insight and documentation by visiting the flexbox guide on MDN. I encourage you to go experiment and get familiar, but I won’t bombard you with any more theory. Let’s look at how flexbox has evolved over the years.

A History of Flexbox

Flexbox is now becoming more widely used due to its increasing support as the days roll by, but it has actually been around since 2009. With that in mind, there’s a lot of documentation and examples around the web these days that utilise old versions (although this is starting to fade out).

In a nutshell:

  • The 2009 spec was released, and with it came all the box- type declarations. If you see any tutorials or example CSS that use box-* type properties, you’re looking at the initial, now outdated version of flexbox. Here’s the property index from the 2009 spec.
  • In 2011, the spec awkwardly changed for a bit. A flex container was defined using display: flexbox, or display: inline-flexbox (which you can see here). There was also a flex() function.
  • In 2012, the spec was updated to what we know today. If you see the property display: flex on a flex container, then you’re with the times.

It looks like the current version is here to stay, and it is very comprehensive. Here’s the current spec from the W3C that contains every detail.

Flexbox in Action

That’s enough talk about flexbox, let’s now take a look at a basic example. Here’s our markup:

<div class="container">
  <div class="item">
    <h2>Item 1</h2>
  <div class="item">
    <h2>Item 2</h2>
  <div class="item">
    <h2>Item 3</h2>
  <div class="item">
    <h2>Item 4</h2>

And here’s the CSS to put flexbox in action:

.container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;

.item {
  padding: 20px;
  width: 22%;
  background-color: rgb(255,150,100);

This makes the .container element our flex container, and the .item elements our flex items. Here’s a CodePen demo:

See the Pen imJGz by SitePoint (@SitePoint) on CodePen.

This all seems well and simple enough, but don’t get too excited. We have quite a few things we need to consider before using this CSS feature.

Browser Support and Polyfills

It’s pleasing to know that browser support is high and increasing, and we can see the breakdown by having a look at flexbox on Can I use…. It’s supported in IE10 and higher, and across all other browsers except Opera Mini. This is pretty awesome to see. If you’re looking out for IE9 and below though, you’ll need to go down the polyfill/fallback route.

Unfortunately, the only polyfill available is Flexie, which enables the 2009 flexbox model on unsupported browsers. There are no polyfills for the new syntax (although Richard Herrera, who created the original flexbox polyfill is working on one for the updated syntax). In any case, you’ll find yourself wanting to stay clear of polyfills to begin with, as they tend to be slow.

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Fallbacks should be generally easy to implement. Modernizr, a feature detection tool, allows us to detect if a browser supports flexbox (legacy and current), so targeting should be easy, and should look something like this:

.container {
  display: block;

.flexbox .container {
  display: flex;

If Modernizr isn’t your thing, and you’re not heading down the Opera road, then conditional CSS may be all you’ll need to help you sort things out for IE9 and down.

Vendor Prefixes

The syntax for flexbox as shown above looks concise and pretty, but that’s because I haven’t even begun to talk about vendor prefixing. Flexbox is a near nightmare with vendor prefixing, and that’s mainly due to the fact that the spec has changed 3 times in 3 years. Older WebKit browsers are still using webkit-prefixed properties, and some of them are still using the 2009 implementation.

If you need to support all these older implementations, you’ll need a host of *-box, *-flexbox, and *-flex prefixes. The compiled CSS for our .container would look like this:

.container {
  display: -webkit-box;
  display: -webkit-flex;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-pack: justify;
  -webkit-justify-content: space-between;
  -ms-flex-pack: justify;
  justify-content: space-between;
  -webkit-box-align: center;
  -webkit-align-items: center;
  -ms-flex-align: center;
  align-items: center;
  -webkit-flex-wrap: wrap;
  -ms-flex-wrap: wrap;
  flex-wrap: wrap;

That’s not pretty! But there are solutions at our disposal.


Autoprefixer is a great and up-to-date tool that will automatically prefix your CSS for you. You can set it up as a Grunt task, and have it watch your stylesheet for changes. It’s a beautiful tool, and will save you tons of headaches.

Sass and Compass

Sass can also come to the rescue here, as long as we set up some mixins to get us going. Here’s a set of Sass mixins and a basic implementation, taken from CSS-Tricks’ guide to flexbox:

@mixin flexbox() {
  display: -webkit-box;
  display: -moz-box;
  display: -ms-flexbox;
  display: -webkit-flex;
  display: flex;

@mixin flex($values) {
  -webkit-box-flex: $values;
  -moz-box-flex:  $values;
  -webkit-flex:  $values;
  -ms-flex:  $values;
  flex:  $values;

@mixin order($val) {
  -webkit-box-ordinal-group: $val;  
  -moz-box-ordinal-group: $val;     
  -ms-flex-order: $val;     
  -webkit-order: $val;  
  order: $val;

.container {
  @include flexbox();

.item {
  @include flex(1 200px);
  @include order(2);

Compass is a CSS authoring framework that offers a ton of mixins for authoring our Sass files. They do have a mixin for flexbox, but unfortunately it’s for the old syntax. However, Autoprefixer (mentioned above) integrates nicely with Compass, and handles all the prefixing for you without having to change your workflow. Neat.

Finally, if you’re using PHP as your CSS preprocessor, you might want to have a look at Flexbox Functions that provides some easy-to-use methods for dealing with the various parts of flexbox.

So… Are We Ready to Use Flexbox?

We looked at what flexbox is, where it came from, how to use it, support, fallbacks, prefixing, and the works. But still, we have to ask ourselves if we’re ready to start implementing it in our projects. For me, the answer is a resounding Yes. But that resounding yes has some underlying emphasis:

  1. Know your project, your desired outcome, and your target market. If you’re publishing HTML5 mobile apps, then go for it. If you’re developing an accounting system for a business using Windows 98, you’ll probably need to stay away!
  2. Understand that polyfilling the old version might help you out, but will slow down the already-slow browsers. In general, I recommend staying away from polyfills — there’s no point further slowing down an already old system.

So go on out there and learn, practice, and implement flexbox in your next suitable project. It’s a fantastic and powerful feature, and is a lot of fun to use.

I'm a web designer & developer from Trinidad & Tobago, with a degree in Mechanical Engineering. I love the logical side of the web, and I'm an artist/painter at heart. I endorse progressive web techniques, and try to learn something every day. I try to impart my knowledge as much as possible on my personal blog, I love food, I surf every weekend, and I have an amazing creative partnership with fellow mischief maker Elena. Together, we run SAYSM.

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