html - Pseudo elements breaking justify-content: space-between in flexbox layout

Question

I have three divs inside a parent div that are being spaced out using:

display: flex;
justify-content: space-between;

However, the parent div has an :after on it which is making the three divs not go out to the edge of parent div. Is there a way to have flexbox ignore the :before and :after?

codepen.io

.container {
  width: 100%;
  display: flex;
  justify-content: space-between;
  padding-top: 50px;
  background: gray;
}

.container div {
    background: red;
    height: 245px;
    width: 300px;
  }
.container:before {
    content: '';
    display: table;
  }
.container:after {
    clear: both;
    content: '';
    display: table;
  }

<div class="container">
  <div></div>
  <div></div>
  <div></div>
</div>

Answer 1

Short Answer

In CSS, there is currently no 100% reliable way to prevent pseudo-elements from impacting the justify-content: space-between calculation.

Explanation

::before and ::after pseudo elements on a flex container become flex items.

From the spec:

4. Flex Items

Each in-flow child of a flex container becomes a flex item.

In other words, each child of a flex container that is in the normal flow (i.e., not absolutely positioned), is considered a flex item.

Most, if not all, browsers interpret this to include pseudo-elements. The ::before pseudo is the first flex item. The ::after item is the last.

Here is further confirmation of this rendering behavior from Firefox documentation:

In-flow ::after and ::before pseudo-elements are now flex items (bug 867454).

One possible solution to your problem is to remove the pseudo-elements from the normal flow with absolute positioning. However, this method may not work in all browsers:

• Absolutely positioned flex item is not removed from normal flow in Firefox & IE11

See my answer here for illustrations of pseudo elements messing up justify-content:

• justify-content: space-between failing to align elements as expected