This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

This is a property of the original CSS Flexible Box Layout Module draft, and has been replaced by a newer standard. See flexbox for information about the current standard.

The box-flex-group CSS property assigns the flexbox's child elements to a flex group.

/* <integer> values */
box-flex-group: 1;
box-flex-group: 5;

/* Global values */
box-flex-group: inherit;
box-flex-group: initial;
box-flex-group: unset;

For flexible elements assigned to flex groups, the first flex group is 1 and higher values specify subsequent flex groups. The initial value is 1. When dividing up the box's extra space, the browser first considers all elements within the first flex group. Each element within that group is given extra space based on the ratio of that element's flexibility compared to the flexibility of other elements within the same flex group. If the space of all flexible children within the group has been increased to the maximum, the process repeats for the children within the next flex group, using any space left over from the previous flex group. Once there are no more flex groups, and there is still space remaining, the extra space is divided within the containing box according to the box-pack property.

If the box would overflow after the preferred space of the children has been computed, then space is removed from flexible elements in a manner similar to that used when adding extra space. Each flex group is examined in turn and space is removed according to the ratio of the flexibility of each element. Elements do not shrink below their minimum widths.

Initial value1
Applies toin-flow children of box elements
Computed valueas specified
Animation typediscrete
Canonical orderthe unique non-ambiguous order defined by the formal grammar


The box-flex-group property is specified as any positive <integer>.

Formal syntax



Browser compatibility

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support (Yes)-webkit ? No support (Yes)-webkit 1.1-khtml
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support ? ? ? No support ? 1.0-webkit

See also

box-flex, box-ordinal-group, box-pack

Document Tags and Contributors

Contributors to this page: mfluehr, wbamberg, Sebastianz, jwhitlock, Jeremie, velvel53, Sheppy, scottrowe
Last updated by: mfluehr,