CSS flex-basis Property Reference

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

Updated 2026-08-12

flex-basis overview

The CSS flex-basis 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-basis formal syntax

Field	Value
Formal syntax	content \| <'width'>
Initial value	auto
Applies to	flexItemsAndInFlowPseudos
Inherited	No
Percentages	referToFlexContainersInnerMainSize
Computed value	asSpecifiedRelativeToAbsoluteLengths
Animation type	lpc
Media	visual
Specification group	CSS Flexible Box Layout
Status	Standard

Practical examples

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

flex-basis live example

CSS

.reset-example {
  flex-basis: initial;
}

.inherit-example {
  flex-basis: inherit;
}

@supports (flex-basis: initial) {
  .supported {
    flex-basis: initial;
  }
}