order

In the above demo, select the options on the left-hand side to change the value of the pink box's order property. The light blue boxes have been given fixed order values.

Bear in mind the effect of source order. For example, when order: 2; is selected, the pink box is placed before the two blue boxes with order: 2;. This is because the pink box appears before the blue boxes in the source code.

/* <integer> values */
order: 5;
order: -5;

/* Global values */
order: inherit;
order: initial;
order: revert;
order: revert-layer;
order: unset;

Since order is only meant to affect the visual order of elements and not their logical or tab order. order must not be used on non-visual media such as speech.

Defined in the CSS display module, this property impacts only grid and flex items. When order is set on an element whose parent's display property is not creating a flex or grid container, the order property has no effect.

<integer>

Represents the ordinal group to be used by the item.

Using the order property will create a disconnect between the visual presentation of content and DOM order. This will adversely affect low vision users navigating with the aid of assistive technology such as a screen reader. If the visual order differs from the DOM order, your users will have different experiences depending on how they access your content.

• Flexbox & the keyboard navigation disconnect via Tink (2016)
• Source Order Matters via Adrian Roselli (2015)
• Understanding WCAG, Guideline 1.3 explanations
• Understanding Success Criterion 1.3.2 | W3C Understanding WCAG 2.0

order = 
  <integer>  

In this example, we create a classic two-sidebar layout.

HTML

We include a header, a footer, and a main content area. The main content includes an article and two side bars. Note their order! We'll use the CSS order property to change their visual order.

<header>Header</header>
<main>
  <article>Article</article>
  <nav>Nav</nav>
  <aside>Aside</aside>
</main>
<footer>Footer</footer>

CSS

We style the main area using flexible box layout module features; by setting display to flex, the <main> element becomes a flex container. By default, this creates flex items of equal vertical size. The sidebars are both given an absolute width, while the <article> will consume all the positive free space with a flex-grow factor set via the flex shorthand.

We then set different order property values on each of the flex container's three children; this means the CSS is defining that component's visual order rather than it appearing in the order declared in the HTML.

main {
  display: flex;
  text-align: center;
}
main > article {
  flex: 1;
  order: 2;
}
main > nav {
  width: 200px;
  order: 1;
}
main > aside {
  width: 200px;
  order: 3;
}

Result

The <article> appears first in the source order but visually rendered in the center.

• Basic concepts of flexbox
• Ordering flex items
• CSS grid layout and accessibility
• CSS display module