A Guide To Flexbox CSS Tricks
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A Complete Guide to Flexbox | CSS-Tricks
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A Complete Guide to Flexbox
BY CHRIS COYIER LAST UPDATED ON AUGUST 22, 2018
FLEXBOX, LAYOUT
▶ Background
▶ Basics & Terminology
container
Properties for the Parent
(flex container)
# display
This defines a flex container; inline or block depending on the given value. It enables a
flex context for all its direct children.
CSS
.container {
display: flex; /* or inline-flex */
}
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Note that CSS columns have no effect on a flex container.
# flex-direction
This establishes the main-axis, thus defining the direction flex items are placed in the
flex container. Flexbox is (aside from optional wrapping) a single-direction layout
concept. Think of flex items as primarily laying out either in horizontal rows or vertical
columns.
CSS
.container {
flex-direction: row | row-reverse | column | column-rever
}
row (default): left to right in ltr ; right to left in rtl
row-reverse : right to left in ltr ; left to right in rtl
column : same as row but top to bottom
column-reverse : same as row-reverse but bottom to top
# flex-wrap
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By default, flex items will all try to fit onto one line. You can change that and allow the
items to wrap as needed with this property.
CSS
.container{
flex-wrap: nowrap | wrap | wrap-reverse;
}
nowrap (default): all flex items will be on one line
wrap : flex items will wrap onto multiple lines, from top to bottom.
wrap-reverse : flex items will wrap onto multiple lines from bottom to top.
There are some visual demos of flex-wrap here.
# flex-flow (Applies to: parent flex container element)
This is a shorthand flex-direction and flex-wrap properties, which together define
the flex container's main and cross axes. Default is row nowrap .
CSS
flex-flow: <‘flex-direction’> || <‘flex-wrap’>
# justify-content
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flex-start
flex-end
center
space-between
space-around
space-evenly
This defines the alignment along the main axis. It helps distribute extra free space left
over when either all the flex items on a line are inflexible, or are flexible but have reached
their maximum size. It also exerts some control over the alignment of items when they
overflow the line.
CSS
.container {
justify-content: flex-start | flex-end | center | space-b
}
flex-start (default): items are packed toward the start line
flex-end : items are packed toward to end line
center : items are centered along the line
space-between : items are evenly distributed in the line; first item is on the start
line, last item on the end line
space-around : items are evenly distributed in the line with equal space around
them. Note that visually the spaces aren't equal, since all the items have equal
space on both sides. The first item will have one unit of space against the
container edge, but two units of space between the next item because that next
item has its own spacing that applies.
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space-evenly : items are distributed so that the spacing between any two items
(and the space to the edges) is equal.
# align-items
flex-start
flex-end
center
stretch
baseline
text text
text text
text text
text text
This defines the default behaviour for how flex items are laid out along the cross axis on
the current line. Think of it as the justify-content version for the cross-axis
(perpendicular to the main-axis).
CSS
.container {
align-items: flex-start | flex-end | center | baseline |
}
flex-start : cross-start margin edge of the items is placed on the cross-start
line
flex-end : cross-end margin edge of the items is placed on the cross-end line
center : items are centered in the cross-axis
baseline : items are aligned such as their baselines align
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stretch (default): stretch to fill the container (still respect min-width/max-
width)
# align-content
flex-start
flex-end
center
stretch
space-between
space-around
This aligns a flex container's lines within when there is extra space in the cross-axis,
similar to how justify-content aligns individual items within the main-axis.
Note: this property has no effect when there is only one line of flex items.
CSS
.container {
align-content: flex-start | flex-end | center | space-bet
}
flex-start : lines packed to the start of the container
flex-end : lines packed to the end of the container
center : lines packed to the center of the container
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space-between : lines evenly distributed; the first line is at the start of the
container while the last one is at the end
space-around : lines evenly distributed with equal space around each line
stretch (default): lines stretch to take up the remaining space
items
Properties for the Children
(flex items)
# order
1
1
-1
1
1
2
2
3
5
2
2
99
By default, flex items are laid out in the source order. However, the order property
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controls the order in which they appear in the flex container.
CSS
.item {
order: ; /* default is 0 */
}
# flex-grow
1
1
1
2
1
1
This defines the ability for a flex item to grow if necessary. It accepts a unitless value that
serves as a proportion. It dictates what amount of the available space inside the flex
container the item should take up.
If all items have flex-grow set to 1, the remaining space in the container will be
distributed equally to all children. If one of the children has a value of 2, the remaining
space would take up twice as much space as the others (or it will try to, at least).
CSS
.item {
flex-grow: ; /* default 0 */
}
Negative numbers are invalid.
# flex-shrink
This defines the ability for a flex item to shrink if necessary.
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CSS
.item {
flex-shrink: ; /* default 1 */
}
Negative numbers are invalid.
# flex-basis
This defines the default size of an element before the remaining space is distributed. It
can be a length (e.g. 20%, 5rem, etc.) or a keyword. The auto keyword means "look at
my width or height property" (which was temporarily done by the main-size keyword
until deprecated). The content keyword means "size it based on the item's content" this keyword isn't well supported yet, so it's hard to test and harder to know what its
brethren max-content , min-content , and fit-content do.
CSS
.item {
flex-basis: | auto; /* default auto */
}
If set to 0 , the extra space around content isn't factored in. If set to auto , the extra
space is distributed based on its flex-grow value. See this graphic.
# flex
This is the shorthand for flex-grow, flex-shrink and flex-basis combined. The
second and third parameters ( flex-shrink and flex-basis ) are optional. Default is
0 1 auto .
CSS
.item {
flex: none | [ <'flex-grow'> <'flex-shrink'>? || <'flex-b
}
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It is recommended that you use this shorthand property rather than set the individual
properties. The short hand sets the other values intelligently.
# align-self
flex-start
flex-end
This allows the default alignment (or the one specified by align-items ) to be
overridden for individual flex items.
Please see the align-items explanation to understand the available values.
CSS
.item {
align-self: auto | flex-start | flex-end | center | basel
}
Note that float , clear and vertical-align have no effect on a flex item.
#
Examples
Let's start with a very very simple example, solving an almost daily problem: perfect centering. It
couldn't be any simpler if you use flexbox.
CSS
.parent {
display: flex;
height: 300px; /* Or whatever */
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}
.child {
width: 100px;
/* Or whatever */
height: 100px; /* Or whatever */
margin: auto;
/* Magic! */
}
This relies on the fact a margin set to `auto` in a flex container absorb extra space. So setting a
vertical margin of auto will make the item perfectly centered in both axis.
Now let's use some more properties. Consider a list of 6 items, all with a fixed dimensions in a
matter of aesthetics but they could be auto-sized. We want them to be evenly and nicely
distributed on the horizontal axis so that when we resize the browser, everything is fine (without
media queries!).
CSS
.flex-container {
/* We first create a flex layout context */
display: flex;
/* Then we define the flow direction
and if we allow the items to wrap
* Remember this is the same as:
* flex-direction: row;
* flex-wrap: wrap;
*/
flex-flow: row wrap;
/* Then we define how is distributed the remaining space */
justify-content: space-around;
}
Done. Everything else is just some styling concern. Below is a pen featuring this example. Be sure
to go to CodePen and try resizing your windows to see what happens.
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Let's try something else. Imagine we have a right-aligned navigation on the very top of our
website, but we want it to be centered on medium-sized screens and single-columned on small
devices. Easy enough.
CSS
/* Large */
.navigation {
display: flex;
flex-flow: row wrap;
/* This aligns items to the end line on main-axis */
justify-content: flex-end;
}
/* Medium screens */
@media all and (max-width: 800px) {
.navigation {
/* When on medium sized screens, we center it by evenly dist
justify-content: space-around;
}
}
/* Small screens */
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@media all and (max-width: 500px) {
.navigation {
/* On small screens, we are no longer using row direction bu
flex-direction: column;
}
}
Let's try something even better by playing with flex items flexibility! What about a mobile-first 3columns layout with full-width header and footer. And independent from source order.
CSS
.wrapper {
display: flex;
flex-flow: row wrap;
}
/* We tell all items to be 100% width, via flex-basis */
.wrapper > * {
flex: 1 100%;
}
/* We rely on source order for mobile-first approach
* in this case:
* 1. header
* 2. article
* 3. aside 1
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* 4. aside 2
* 5. footer
*/
/* Medium screens */
@media all and (min-width: 600px) {
/* We tell both sidebars to share a row */
.aside { flex: 1 auto; }
}
/* Large screens */
@media all and (min-width: 800px) {
/* We invert order of first sidebar and main
* And tell the main element to take twice as much width as th
*/
.main { flex: 2 0px; }
.aside-1 { order: 1; }
.main
{ order: 2; }
.aside-2 { order: 3; }
.footer
{ order: 4; }
}
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▶ Prefixing Flexbox
▶ Related Properties
▶ Other Resources
▶ Bugs
#
Browser Support
Broken up by "version" of flexbox:
(new) means the recent syntax from the specification (e.g. display: flex; )
(tweener) means an odd unofficial syntax from 2011 (e.g. display: flexbox; )
(old) means the old syntax from 2009 (e.g. display: box; )
Chrome: 20- (old)
21+ (new)
IE: 10 (tweener)
11+ (new)
Safari: 3.1+ (old)
6.1+ (new)
Edge: 17+ (new)
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Firefox: 2-21 (old)
22+ (new)
Android: 2.1+ (old)
4.4+ (new)
Opera: 12.1+ (new)
iOS: 3.2+ (old)
7.1+ (new)
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Blackberry browser 10+ supports the new syntax.
For more informations about how to mix syntaxes in order to get the best browser support,
please refer to this article (CSS-Tricks) or this article (DevOpera).
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