CSS flex Property Reference

The CSS flex property is a standard property in CSS Flexible Box Layout. Review its formal syntax, computed behavior, and practical declarations.

Updated 2026-08-12

flex overview

The CSS flex property is a standard property in CSS Flexible Box Layout. Review its formal syntax, computed behavior, and practical declarations.

The property is not inherited by default. Use an explicit global keyword when inheritance is intended.

Syntax and formal definition

flex formal syntax

Field	Value
Formal syntax	none \| [ <'flex-grow'> <'flex-shrink'>? \|\| <'flex-basis'> ]
Initial value	flex-grow, flex-shrink, flex-basis
Applies to	flexItemsAndInFlowPseudos
Inherited	No
Percentages	no
Computed value	flex-grow, flex-shrink, flex-basis
Animation type	flex-grow, flex-shrink, flex-basis
Media	visual
Specification group	CSS Flexible Box Layout
Status	Standard

Practical examples

These declarations demonstrate valid ways to set flex. The initial and inherit global keywords remain available even when a property-specific value is preferable.

flex live example

CSS

.reset-example {
  flex: initial;
}

.inherit-example {
  flex: inherit;
}

@supports (flex: 1 1 auto) {
  .supported {
    flex: 1 1 auto;
  }
}