Flex utilities can be used to apply flexbox behaviors to elements by using utility classes.
Required reading
Before using these utilities, you should be familiar with CSS3 Flexible Box spec. If you are not, check out MDN’s guide:
:book: Using CSS Flexible Boxes
Flex container
Use these classes to make an element lay out its content using the flexbox model. Each direct child of the flex container will become a flex item.
CSS
.d-flex { display: flex; }
.d-inline-flex { display: inline-flex; }
Classes
| Class | Description |
|---|---|
.d-flex |
The element behaves like a block and lays out its content using the flexbox model. |
.d-inline-flex |
The element behaves like an inline element and lays out its content using the flexbox model. |
Example using .d-flex
<!-- flex container -->
<div class="border d-flex">
<div class="p-5 border bg-gray-light">flex item 1</div>
<div class="p-5 border bg-gray-light">flex item 2</div>
<div class="p-5 border bg-gray-light">flex item 3</div>
</div>
Example using .d-inline-flex
<!-- inline-flex container -->
<div class="border d-inline-flex">
<div class="p-5 border bg-gray-light">flex item 1</div>
<div class="p-5 border bg-gray-light">flex item 2</div>
<div class="p-5 border bg-gray-light">flex item 3</div>
</div>
Flex direction
Use these classes to define the orientation of the main axis (row or column). By default, flex items will display in a row. Use .flex-column to change the direction of the main axis to vertical.
CSS
.flex-row { flex-direction: row; }
.flex-row-reverse { flex-direction: row-reverse; }
.flex-column { flex-direction: column; }
Classes
| Class | Description |
|---|---|
.flex-row |
The main axis runs left to right (default). |
.flex-row-reverse |
The main axis runs right to left. |
.flex-column |
The main axis runs top to bottom. |
Example using .flex-column
<div class="border d-flex flex-column">
<div class="p-5 border bg-gray-light">Item 1</div>
<div class="p-5 border bg-gray-light">Item 2</div>
<div class="p-5 border bg-gray-light">Item 3</div>
</div>
Example using .flex-row
This example uses the responsive variant .flex-md-row to override .flex-column Learn more about responsive flexbox utilities here.
<div class="border d-flex flex-column flex-md-row">
<div class="p-5 border bg-gray-light">Item 1</div>
<div class="p-5 border bg-gray-light">Item 2</div>
<div class="p-5 border bg-gray-light">Item 3</div>
</div>
Example using .flex-row-reverse
This example uses the responsive variant .flex-md-row-reverse to override .flex-column Learn more about responsive flexbox utilities here.
<div class="border d-flex flex-column flex-md-row-reverse">
<div class="p-5 border bg-gray-light">Item 1</div>
<div class="p-5 border bg-gray-light">Item 2</div>
<div class="p-5 border bg-gray-light">Item 3</div>
</div>
Flex wrap
You can choose whether flex items are forced into a single line or wrapped onto multiple lines.
CSS
.flex-wrap { flex-wrap: wrap; }
.flex-nowrap { flex-wrap: nowrap; }
Classes
| Class | Description |
|---|---|
.flex-wrap |
Flex items will break onto multiple lines (default) |
.flex-nowrap |
Flex items are laid out in a single line, even if they overflow |
flex-wrap example
<div class="border d-flex flex-wrap">
<div class="p-5 px-6 border bg-gray-light">1</div>
<div class="p-5 px-6 border bg-gray-light">2</div>
<div class="p-5 px-6 border bg-gray-light">3</div>
<div class="p-5 px-6 border bg-gray-light">4</div>
<div class="p-5 px-6 border bg-gray-light">5</div>
<div class="p-5 px-6 border bg-gray-light">6</div>
<div class="p-5 px-6 border bg-gray-light">7</div>
<div class="p-5 px-6 border bg-gray-light">8</div>
<div class="p-5 px-6 border bg-gray-light">9</div>
</div>
flex-nowrap example
<div class="border d-flex flex-nowrap">
<div class="p-5 px-6 border bg-gray-light">1</div>
<div class="p-5 px-6 border bg-gray-light">2</div>
<div class="p-5 px-6 border bg-gray-light">3</div>
<div class="p-5 px-6 border bg-gray-light">4</div>
<div class="p-5 px-6 border bg-gray-light">5</div>
<div class="p-5 px-6 border bg-gray-light">6</div>
<div class="p-5 px-6 border bg-gray-light">7</div>
<div class="p-5 px-6 border bg-gray-light">8</div>
<div class="p-5 px-6 border bg-gray-light">9</div>
</div>
Justify content
Use these classes to distribute space between and around flex items along the main axis of the container.
CSS
.flex-justify-start { justify-content: flex-start; }
.flex-justify-end { justify-content: flex-end; }
.flex-justify-center { justify-content: center; }
.flex-justify-between { justify-content: space-between; }
.flex-justify-around { justify-content: space-around; }
Classes
| Class | Default behavior |
|---|---|
.flex-justify-start |
Justify all items to the left |
.flex-justify-end |
Justify all items to the right |
.flex-justify-center |
Justify items to the center of the container |
.flex-justify-between |
Distribute items evenly. First item is on the start line, last item is on the end line. |
.flex-justify-around |
Distribute items evenly with equal space around them |
flex-justify-start
Use .flex-justify-start to align items to the start line. By default this will be on the left side of the container. If you are using .flex-column, the end line will be at the top of the container.
<div class="border d-flex flex-justify-start">
<div class="p-5 border bg-gray-light">1</div>
<div class="p-5 border bg-gray-light">2</div>
<div class="p-5 border bg-gray-light">3</div>
</div>
flex-justify-end
Use .flex-justify-end to align items to the end line. By default this will be on the right side of the container. If you are using .flex-column, the end line will be at the bottom of the container.
<div class="border d-flex flex-justify-end">
<div class="p-5 border bg-gray-light">1</div>
<div class="p-5 border bg-gray-light">2</div>
<div class="p-5 border bg-gray-light">3</div>
</div>
flex-justify-center
Use .flex-justify-center to align items in the middle of the container.
<div class="border d-flex flex-justify-center">
<div class="p-5 border bg-gray-light">1</div>
<div class="p-5 border bg-gray-light">2</div>
<div class="p-5 border bg-gray-light">3</div>
</div>
flex-justify-between
Use .flex-justify-between to distribute items evenly in the container. The first items will be on the start line and the last item will be on the end line.
<div class="border d-flex flex-justify-between">
<div class="p-5 border bg-gray-light">1</div>
<div class="p-5 border bg-gray-light">2</div>
<div class="p-5 border bg-gray-light">3</div>
</div>
flex-justify-around
Use .flex-justify-around to distribute items evenly, with an equal amount of space around them. Visually the spaces won’t look equal, since each item has the same unit of space around it. For example, the first item only has one unit of space between it and the start line, but it has two units of space between it and the next item.
<div class="border d-flex flex-justify-around">
<div class="p-5 border bg-gray-light">1</div>
<div class="p-5 border bg-gray-light">2</div>
<div class="p-5 border bg-gray-light">3</div>
</div>
Align items
Use these classes to align items on the cross axis.
The cross axis runs perpendicular to the main axis. By default the main axis runs horizontally, so your items will align vertically on the cross axis. If you use flex-column to make the main axis run vertically, your items will be aligned horizontally.
CSS
.flex-items-start { align-items: flex-start; }
.flex-items-end { align-items: flex-end; }
.flex-items-center { align-items: center; }
.flex-items-baseline { align-items: baseline; }
.flex-items-stretch { align-items: stretch; }
Classes
| Class | Behavior |
|---|---|
.flex-items-start |
Align items to the start of the cross axis |
.flex-items-end |
Align items to the end of the cross axis |
.flex-items-center |
Align items to the center of the cross axis |
.flex-items-baseline |
Align items along their baselines |
.flex-items-stretch |
Stretch items from start of cross axis to end of cross axis |
flex-items-start
<div style="min-height: 150px;" class="border d-flex flex-items-start">
<div class="p-5 border bg-gray-light">1</div>
<div class="p-5 border bg-gray-light">2</div>
<div class="p-5 border bg-gray-light">3</div>
<div class="p-5 border bg-gray-light">4</div>
</div>
flex-items-end
<div style="min-height: 150px;" class="border d-flex flex-items-end">
<div class="p-5 border bg-gray-light">1</div>
<div class="p-5 border bg-gray-light">2</div>
<div class="p-5 border bg-gray-light">3</div>
<div class="p-5 border bg-gray-light">4</div>
</div>
flex-items-center
<div style="min-height: 150px;" class="border d-flex flex-items-center">
<div class="p-5 border bg-gray-light">1</div>
<div class="p-5 border bg-gray-light">2</div>
<div class="p-5 border bg-gray-light">3</div>
<div class="p-5 border bg-gray-light">4</div>
</div>
flex-items-baseline
With .flex-items-baseline, items will be aligned along their baselines even if they have different font sizes.
<div style="min-height: 150px;" class="border d-flex flex-items-baseline">
<div class="p-5 border bg-gray-light f1">1</div>
<div class="p-5 border bg-gray-light">2</div>
<div class="p-5 border bg-gray-light f3">3</div>
<div class="p-5 border bg-gray-light">4</div>
</div>
flex-items-stretch
<div style="min-height: 150px;" class="border d-flex flex-items-stretch">
<div class="p-5 border bg-gray-light">1</div>
<div class="p-5 border bg-gray-light">2</div>
<div class="p-5 border bg-gray-light">3</div>
<div class="p-5 border bg-gray-light">4</div>
</div>
Align content
When the main axis wraps, this creates multiple main axis lines and adds extra space in the cross axis. Use these classes to align the lines of the main axis on the cross axis.
CSS
.flex-content-start { align-content: flex-start; }
.flex-content-end { align-content: flex-end; }
.flex-content-center { align-content: center; }
.flex-content-between { align-content: space-between; }
.flex-content-around { align-content: space-around; }
.flex-content-stretch { align-content: stretch; }
Classes
| Class | Description |
|---|---|
.flex-content-start |
Align content to the start of the cross axis |
.flex-content-end |
Align content to the end of the cross axis |
.flex-content-center |
Align content to the center of the cross axis |
.flex-content-between |
Distribute content evenly. First line is on the start of the cross axis, last line is on the end of the cross axis. |
.flex-content-around |
Stretch items from the start of the cross axis to the end of the cross axis. |
.flex-content-stretch |
Lines stretch to occupy available space. |
flex-content-start
<div style="min-height: 300px;" class="border d-flex flex-wrap flex-content-start">
<div class="p-5 border bg-gray-light">1</div>
<div class="p-5 border bg-gray-light">2</div>
<div class="p-5 border bg-gray-light">3</div>
<div class="p-5 border bg-gray-light">4</div>
<div class="p-5 border bg-gray-light">5</div>
<div class="p-5 border bg-gray-light">6</div>
<div class="p-5 border bg-gray-light">7</div>
<div class="p-5 border bg-gray-light">8</div>
<div class="p-5 border bg-gray-light">9</div>
<div class="p-5 border bg-gray-light">10</div>
<div class="p-5 border bg-gray-light">11</div>
<div class="p-5 border bg-gray-light">12</div>
</div>
flex-content-end
<div style="min-height: 300px;" class="border d-flex flex-wrap flex-content-end">
<div class="p-5 border bg-gray-light">1</div>
<div class="p-5 border bg-gray-light">2</div>
<div class="p-5 border bg-gray-light">3</div>
<div class="p-5 border bg-gray-light">4</div>
<div class="p-5 border bg-gray-light">5</div>
<div class="p-5 border bg-gray-light">6</div>
<div class="p-5 border bg-gray-light">7</div>
<div class="p-5 border bg-gray-light">8</div>
<div class="p-5 border bg-gray-light">9</div>
<div class="p-5 border bg-gray-light">10</div>
<div class="p-5 border bg-gray-light">11</div>
<div class="p-5 border bg-gray-light">12</div>
</div>
flex-content-center
<div style="min-height: 300px;" class="border d-flex flex-wrap flex-content-center">
<div class="p-5 border bg-gray-light">1</div>
<div class="p-5 border bg-gray-light">2</div>
<div class="p-5 border bg-gray-light">3</div>
<div class="p-5 border bg-gray-light">4</div>
<div class="p-5 border bg-gray-light">5</div>
<div class="p-5 border bg-gray-light">6</div>
<div class="p-5 border bg-gray-light">7</div>
<div class="p-5 border bg-gray-light">8</div>
<div class="p-5 border bg-gray-light">9</div>
<div class="p-5 border bg-gray-light">10</div>
<div class="p-5 border bg-gray-light">11</div>
<div class="p-5 border bg-gray-light">12</div>
</div>
flex-content-between
<div style="min-height: 300px;" class="border d-flex flex-wrap flex-content-between">
<div class="p-5 border bg-gray-light">1</div>
<div class="p-5 border bg-gray-light">2</div>
<div class="p-5 border bg-gray-light">3</div>
<div class="p-5 border bg-gray-light">4</div>
<div class="p-5 border bg-gray-light">5</div>
<div class="p-5 border bg-gray-light">6</div>
<div class="p-5 border bg-gray-light">7</div>
<div class="p-5 border bg-gray-light">8</div>
<div class="p-5 border bg-gray-light">9</div>
<div class="p-5 border bg-gray-light">10</div>
<div class="p-5 border bg-gray-light">11</div>
<div class="p-5 border bg-gray-light">12</div>
</div>
flex-content-around
<div style="min-height: 300px;" class="border d-flex flex-wrap flex-content-around">
<div class="p-5 border bg-gray-light">1</div>
<div class="p-5 border bg-gray-light">2</div>
<div class="p-5 border bg-gray-light">3</div>
<div class="p-5 border bg-gray-light">4</div>
<div class="p-5 border bg-gray-light">5</div>
<div class="p-5 border bg-gray-light">6</div>
<div class="p-5 border bg-gray-light">7</div>
<div class="p-5 border bg-gray-light">8</div>
<div class="p-5 border bg-gray-light">9</div>
<div class="p-5 border bg-gray-light">10</div>
<div class="p-5 border bg-gray-light">11</div>
<div class="p-5 border bg-gray-light">12</div>
</div>
flex-content-stretch
<div style="min-height: 300px;" class="border d-flex flex-wrap flex-content-stretch">
<div class="p-5 border bg-gray-light">1</div>
<div class="p-5 border bg-gray-light">2</div>
<div class="p-5 border bg-gray-light">3</div>
<div class="p-5 border bg-gray-light">4</div>
<div class="p-5 border bg-gray-light">5</div>
<div class="p-5 border bg-gray-light">6</div>
<div class="p-5 border bg-gray-light">7</div>
<div class="p-5 border bg-gray-light">8</div>
<div class="p-5 border bg-gray-light">9</div>
<div class="p-5 border bg-gray-light">10</div>
<div class="p-5 border bg-gray-light">11</div>
<div class="p-5 border bg-gray-light">12</div>
</div>
Flex
Use this class to specify the ability of a flex item to alter its dimensions to fill available space.
.flex-auto { flex: 1 1 auto; }
| Class | Description |
|---|---|
.flex-auto |
Sets default values for flex-grow (1), flex-shrink (1) and flex-basis (auto) |
flex-auto
<div class="border d-flex">
<div class="p-5 border bg-gray-light flex-auto">.flex-auto</div>
<div class="p-5 border bg-gray-light flex-auto">.flex-auto</div>
<div class="p-5 border bg-gray-light flex-auto">.flex-auto</div>
</div>
Align self
Use these classes to adjust the alignment of an individual flex item on the cross axis. This overrides any align-items property applied to the flex container.
CSS
.flex-self-auto { align-self: auto; }
.flex-self-start { align-self: flex-start; }
.flex-self-end { align-self: flex-end; }
.flex-self-center { align-self: center; }
.flex-self-baseline { align-self: baseline; }
.flex-self-stretch { align-self: stretch; }
Classes
| Class | Description |
|---|---|
.flex-self-auto |
Inherit alignment from parent |
.flex-self-start |
Align to the start of the cross axis |
.flex-self-end |
Align to the end of the cross axis |
.flex-self-center |
Align to center of cross axis |
.flex-self-baseline |
Align baseline to the start of the cross axis |
.flex-self-stretch |
Stretch item from start of cross axis to end of cross axis. |
flex-self-auto
<div style="min-height: 150px;" class="border d-flex">
<div class="p-5 border bg-gray-light flex-self-auto">.flex-self-auto</div>
<div class="p-5 border bg-gray-light"> </div>
<div class="p-5 border bg-gray-light"> </div>
</div>
flex-self-start
<div style="min-height: 150px;" class="border d-flex">
<div class="p-5 border bg-gray-light flex-self-start">.flex-self-start</div>
<div class="p-5 border bg-gray-light"> </div>
<div class="p-5 border bg-gray-light"> </div>
</div>
flex-self-end
<div style="min-height: 150px;" class="border d-flex">
<div class="p-5 border bg-gray-light flex-self-end">.flex-self-end</div>
<div class="p-5 border bg-gray-light"> </div>
<div class="p-5 border bg-gray-light"> </div>
</div>
flex-self-center
<div style="min-height: 150px;" class="border d-flex">
<div class="p-5 border bg-gray-light flex-self-center">.flex-self-center</div>
<div class="p-5 border bg-gray-light"> </div>
<div class="p-5 border bg-gray-light"> </div>
</div>
flex-self-baseline
<div style="min-height: 150px;" class="border d-flex flex-items-end">
<div class="p-5 border bg-gray-light flex-self-baseline f4">.flex-self-baseline</div>
<div class="p-5 border bg-gray-light f1">item</div>
<div class="p-5 border bg-gray-light f00">item</div>
</div>
flex-self-stretch
<div style="min-height: 150px;" class="border d-flex flex-items-start">
<div class="p-5 border bg-gray-light flex-self-stretch">.flex-self-stretch</div>
<div class="p-5 border bg-gray-light"> </div>
<div class="p-5 border bg-gray-light"> </div>
</div>
Responsive flex utilities
All flexbox utilities can be adjusted per breakpoint using the following formulas:
d-[breakpoint]-[property]fordisplayflex-[breakpoint]-[property]-[behavior]for various flex propertiesflex-[breakpoint]-item-equalfor equal width and equal height flex items
Each responsive style is applied to the specified breakpoint and up.
Example classes
/* Example classes */
.d-sm-flex {}
.d-md-inline-flex {}
.flex-lg-row {}
.flex-xl-column {}
.flex-sm-wrap {}
.flex-lg-nowrap {}
.flex-lg-self-start {}
.flex-md-item-equal {}
Example usage
Mixing flex properties:
<div style="min-height: 150px;" class="border d-flex flex-items-start flex-md-items-center flex-justify-start flex-lg-justify-between">
<div class="p-5 border bg-gray-light flex-md-self-stretch">.flex-self-stretch</div>
<div class="p-5 border bg-gray-light"> </div>
<div class="p-5 border bg-gray-light"> </div>
</div>
Using the equal width, equal height utilities:
<div class="border d-flex">
<div class="flex-md-item-equal p-3 border bg-gray-light">Stuff and things</div>
<div class="flex-md-item-equal p-3 border bg-gray-light">More stuff<br> on multiple lines</div>
<div class="flex-md-item-equal p-3 border bg-gray-light">Hi mom</div>
</div>
Example components
The flex utilities can be used to create a number of components. Here are some examples.
Media object
You can use flex utilities to make a simple media object, like this:
<div class="border d-flex flex-items-center p-4">
<div class="p-5 border bg-gray-light">image</div>
<p class="pl-4 m-0"><b>Body</b> Bacon ipsum dolor sit amet chuck prosciutto landjaeger ham hock filet mignon shoulder hamburger pig venison.</p>
</div>
Responsive media object
Here is an example of a media object that is vertically centered on large screens, but converts to a stacked column layout on small screens.
<div class="border p-3 d-flex flex-column flex-md-row flex-md-items-center">
<div class="pr-0 pr-md-3 mb-3 mb-md-0 d-flex flex-justify-center flex-md-justify-start">
<img style="max-width:100px; max-height:100px;" src="https://github.com/github.png" />
</div>
<div class="d-flex text-center text-md-left">
<p><b>Body</b> Bacon ipsum dolor sit amet chuck prosciutto landjaeger ham hock filet mignon shoulder hamburger pig venison.</p>
</div>
<div class="ml-md-3 d-flex flex-justify-center">
<%= octicon "mark-github", :height => '32' %>
</div>
</div>
Flexbox bugs
This section lists flexbox bugs that affect browsers we currently support (citation needed).
1. Minimum content sizing of flex items not honored: Some browsers don’t respect flex item size. Instead of respecting the minimum content size, items shrink below their minimum size which can create some undesirable results, such as overflowing text. The workaround is to apply flex-shrink: 0; to the items using d-flex. This can be applied with the flex-shrink-0 utility. For more information read philipwalton/flexbugs.