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CSS flex Property

The flex property specifies how a flex item will grow or shrink so as to fit the space available in its flex container.

The flex property is a shorthand that sets the following properties in a single declaration:

CSS Demo: flex

flex: 1;
flex: 4;
flex: 1 40px;
flex: 3 40px;
flex: 1 1 100px;
Change me
2
3

The flex property can have from one to three values:

  • When one value is specified:
    • If the value is number: then it is interpreted as flex-grow
    • If the value is width: then it is interpreted as flex-basis
  • When two values are specified:
    • The first value must be a number and it is interpreted as flex-grow
    • The second value must be one of:
      • A number that is interpreted as flex-shrink
      • A width: that is interpreted as flex-basis
  • When three values are specified:
    • The first value must be a number and it is interpreted as flex-grow
    • The second value must be a number and it is interpreted as flex-shrink
    • The third value must be a width and it is interpreted as flex-basis

Note: If any property listed above is missing or omitted, the default value for that property will be applied, if any.

Technical Details

Default value
as each of the properties of the shorthand:
  • flex-grow: 0
  • flex-shrink: 1
  • flex-basis: auto
Applies to flex items
Inherited no
Computed value as specified
Animatable yes See animatable properties. Demo
Version CSS3
JavaScript syntax object.style.flex = "3" Demo


CSS Syntax:

flex: flex-grow flex-shrink flex-basis|auto|initial|inherit;

Examples

The following example shows how to use flex property:

Run code

Browser compatibility

The numbers in the table specify the first browser version that fully supports the flex property.

Numbers followed by -webkit- and -moz- specify the first version that worked with a vendor prefix.

Property
flex 29
21 -webkit-
28
18 -moz-
12.1 9
6.1 -webkit-
12

Property Values

The following table describes the values of flex property:

Value Description
flex-grow A number defines the flex-grow of the flex item
flex-shrink A number defines the flex-shrink of the flex item
flex-basis The length of the flex item. Possible values: "auto", "inherit", or a number followed by "%", "px", "em" or any other length unit
auto Interpreted as 1 1 auto
none Interpreted as 0 0 auto
initial Sets this property to its default value
inherit Inherits this property from its parent element

See also

CSS Flexbox Layout

CSS align-content property

CSS align-items property

CSS align-self property

CSS display property

CSS flex-basis property

CSS flex-flow property

CSS flex-grow property

CSS flex-shrink property

CSS flex-direction property

CSS flex-wrap property

CSS justify-content property

CSS order property