flex
The flex
CSS shorthand property sets how a flex item will grow or shrink to fit the space available in its flex container.
Constituent properties
This property is a shorthand for the following CSS properties:
Syntax
/* Keyword values */
flex: auto;
flex: initial;
flex: none;
/* One value, unitless number: flex-grow
flex-basis is then equal to 0. */
flex: 2;
/* One value, width/height: flex-basis */
flex: 10em;
flex: 30%;
flex: min-content;
/* Two values: flex-grow | flex-basis */
flex: 1 30px;
/* Two values: flex-grow | flex-shrink */
flex: 2 2;
/* Three values: flex-grow | flex-shrink | flex-basis */
flex: 2 2 10%;
/* Global values */
flex: inherit;
flex: initial;
flex: revert;
flex: unset;
The flex
property may be specified using one, two, or three values.
- One-value syntax: the value must be one of:
- a
<number>
: In this case it is interpreted asflex: <number> 1 0
; theflex-shrink
value is assumed to be1
and theflex-basis
value is assumed to be0
. - a
<width>
: In this case it is interpreted asflex: 1 1 <width>
; theflex-grow
value is assumed to be1
and theflex-shrink
value is assumed to be1
. - one of the keywords:
none
,auto
, orinitial
.
- a
- Two-value syntax:
- Three-value syntax: the values must be in the following order:
Values
initial
-
The item is sized according to its
width
andheight
properties. It shrinks to its minimum size to fit the container, but does not grow to absorb any extra free space in the flex container. This is equivalent to setting "flex: 0 1 auto
". auto
-
The item is sized according to its
width
andheight
properties, but grows to absorb any extra free space in the flex container, and shrinks to its minimum size to fit the container. This is equivalent to setting "flex: 1 1 auto
". none
-
The item is sized according to its
width
andheight
properties. It is fully inflexible: it neither shrinks nor grows in relation to the flex container. This is equivalent to setting "flex: 0 0 auto
". <'flex-grow'>
-
Defines the
flex-grow
of the flex item. Negative values are considered invalid. Defaults to1
when omitted. (initial is0
) <'flex-shrink'>
-
Defines the
flex-shrink
of the flex item. Negative values are considered invalid. Defaults to1
when omitted. (initial is1
) <'flex-basis'>
-
Defines the
flex-basis
of the flex item. A preferred size of0
must have a unit to avoid being interpreted as a flexibility. Defaults to0
when omitted. (initial isauto
)
Description
For most purposes, authors should set flex
to one of the following values: auto
, initial
, none
, or a positive unitless number. To see the effect of these values, try resizing the flex containers below:
By default flex items don't shrink below their minimum content size. To change this, set the item's min-width
or min-height
.
Formal definition
Initial value | as each of the properties of the shorthand:
|
---|---|
Applies to | flex items, including in-flow pseudo-elements |
Inherited | no |
Computed value | as each of the properties of the shorthand:
|
Animation type | as each of the properties of the shorthand:
|
Formal syntax
Examples
Setting flex: auto
HTML
<div id="flex-container">
<div class="flex-item" id="flex">Flex box (click to toggle raw box)</div>
<div class="raw-item" id="raw">Raw box</div>
</div>
CSS
#flex-container {
display: flex;
flex-direction: row;
}
#flex-container > .flex-item {
flex: auto;
}
#flex-container > .raw-item {
width: 5rem;
}
Result
Specifications
Specification |
---|
CSS Flexible Box Layout Module Level 1 # flex-property |
Browser compatibility
BCD tables only load in the browser
See also
- CSS Flexbox Guide: Basic Concepts of Flexbox
- CSS Flexbox Guide: Controlling Ratios of flex items along the main axis