Why are flex items not wrapping?

Issue

I am attempting to make multiple rows of squares (3 per line) which have the same height.

I have written some HTML and CSS for this but the boxes all go on the same line.

Here's what I have so far:

#list-wrapper {
  display: flex;
  width: 100%;
}
#list-wrapper div {
  width: 33.33%;
}
#list-wrapper div img {
  flex: 1;
}

<div id="list-wrapper">
  <div>
    <img src="images/1.png" alt="image one" />
  </div>
  <div>
    <img src="images/2.png" alt="image two" />
  </div>
  <div>
    <img src="images/1.png" alt="image one" />
  </div>
  <div>
    <img src="images/2.png" alt="image two" />
  </div>
  <div>
    <img src="images/1.png" alt="image one" />
  </div>
  <div>
    <img src="images/2.png" alt="image two" />
  </div>
</div>

When I load the page with this all boxes appear but they are all on one line going over the parent div's 100% width.

Solution

An initial setting of a flex container is flex-wrap: nowrap.

This means that when you create a flex container (by applying display: flex or display: inline-flex to an element) all child elements ("flex items") are confined to a single line.

To enable flex items to wrap use flex-wrap: wrap.

---

Here are a few examples of how flex properties work:

A simple flex container with various flex items containing an image:

#list-wrapper {
    display: flex;
    border: 1px solid black;
}

#list-wrapper div {}

#list-wrapper div img {
    height: 150px;
    width: 150px;
}

<div id="list-wrapper">
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
</div>

Note that only one flex property has been declared: display: flex. This establishes the flex container. The following behaviors are by default:

• flex-wrap: nowrap
• flex-direction: row
• justify-content: flex-start

To allow the items to wrap, add flex-wrap: wrap:

#list-wrapper {
    display: flex;
    flex-wrap: wrap; /* NEW */
    border: 1px solid black;
}

#list-wrapper div { }

#list-wrapper div img {
    height: 150px;
    width: 150px;
}

<div id="list-wrapper">
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
</div>

To allow only three items per row, use the flex property:

#list-wrapper {
    display: flex;
    flex-wrap: wrap;
    border: 1px solid black;
}

#list-wrapper div {
    margin: 10px;
    flex: 1 1 calc(33.33% - 20px); /* flex-grow, flex-shrink, 
                                      flex-basis: (width - margin) */
}

#list-wrapper div img {
    height: 150px;
    width: 150px;
}

<div id="list-wrapper">
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
</div>

Also, all flex items have equal height by default (align-items: stretch).

#list-wrapper {
    display: flex;
    flex-wrap: wrap;
    border: 1px solid black;
}

#list-wrapper div {
    margin: 10px;
    flex: 1 1 calc(33.33% - 30px);
    border: 1px solid #ccc;
    background-color: lightgreen;
    text-align: center;
}

#list-wrapper div img {
    height: 150px;
    width: 150px;
}

<div id="list-wrapper">
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
</div>

The stretch is more noticeable if you restore flex-wrap: nowrap and give the container a height:

#list-wrapper {
    display: flex;
    /* flex-wrap: wrap; */
    border: 1px solid black;
    height: 600px;
}

#list-wrapper div {
    margin: 10px;
    flex: 1 1 calc(33.33% - 30px);
    border: 1px solid #ccc;
    background-color: lightgreen;
    text-align: center;
}

#list-wrapper div img {
    height: 150px;
    width: 150px;
}

<div id="list-wrapper">
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
    <div><img src="http://i.imgur.com/60PVLis.png" alt=""></div>
</div>

Answered By - Michael Benjamin