CSS align-content

The CSS align-content property controls alignment of a box's content along the cross/block axis within its content box.

The alignment is similar to how justify-content aligns individual items, however, align-content aligns the whole line. It aligns flex lines within a multi-line flex container when there is extra space in the cross-axis.

To create a multi-line flex container apply flex-wrap with a value of either wrap or wrap-reverse.

Syntax

Possible Values

flex-start

Flex items are packed toward the start of the line.

flex-end

Flex items are packed toward the end of the line.

center

Flex items are packed toward the center of the line.

space-between

Flex items are evenly distributed in the line.

space-around

Same as space-between, but with half-size spaces on either end.

stretch

Lines stretch to take up the remaining space. If the leftover free-space is negative, this value is identical to flex-start. Otherwise, the free-space is split equally between all of the lines, increasing their cross size.

In addition, all CSS properties also accept the following CSS-wide keyword values as the sole component of their property value:

initial

Represents the value specified as the property's initial value.

inherit

Represents the computed value of the property on the element's parent.

unset

This value acts as either inherit or initial, depending on whether the property is inherited or not. In other words, it sets all properties to their parent value if they are inheritable or to their initial value if not inheritable.

Basic Property Information

Example Code

Basic CSS

Working Example within an HTML Document

About Flexbox

Flexbox refers to the Flexible Box Layout module introduced in CSS3. Flex items are placed within a flex container. A flex container is an element with either display: flex or display: inline-flex.

In the flex layout model, the children of a flex container can be laid out in any direction, and can "flex" their sizes, either growing to fill unused space or shrinking to avoid overflowing the parent.

For more information on flex items, see the flex property.

CSS Specifications

• The align-content property is defined in the CSS Flexible Box Layout Module Level 1 (W3C Candidate Recommendation, 26 May 2016)
• It is also being redefined in CSS Box Alignment Module Level 3 (W3C Working Draft).

Browser Support

The following table provided by Caniuse.com shows the level of browser support for this feature.

Vendor Prefixes

For maximum browser compatibility many web developers add browser-specific properties by using extensions such as -webkit- for Safari, Google Chrome, and Opera (newer versions), -ms- for Internet Explorer, -moz- for Firefox, -o- for older versions of Opera etc. As with any CSS property, if a browser doesn't support a proprietary extension, it will simply ignore it.

This practice is not recommended by the W3C, however in many cases, the only way you can test a property is to include the CSS extension that is compatible with your browser.

The major browser manufacturers generally strive to adhere to the W3C specifications, and when they support a non-prefixed property, they typically remove the prefixed version. Also, W3C advises vendors to remove their prefixes for properties that reach Candidate Recommendation status.

Many developers use Autoprefixer, which is a postprocessor for CSS. Autoprefixer automatically adds vendor prefixes to your CSS so that you don't need to. It also removes old, unnecessary prefixes from your CSS.

You can also use Autoprefixer with preprocessors such as Less and Sass.