Does Setting `display` on Flexbox Items Offer Real Advantages Beyond the Default Behavior?

Exploring the Significance of Display Property in Flex Box Items

Question:

Can adjusting the display property of individual flex box items provide any distinct advantages or outcomes? Specifically, what are the implications of setting display to block or inline-block?

Answer:

The CSS specification clarifies that inline-level display values assigned to flex items will be converted to their block-level counterparts. Therefore, setting display explicitly to block or inline-block will not produce discernible changes since both resolve to block.

However, significant effects can arise when the display property is set to table, inline-table, inline-grid, or grid. In these cases, the flex item will adopt the characteristics of the specified display type, altering its presentation and behavior.

Consider the following HTML and CSS example:

<div class="box">
  <div>
    <span></span>

    <span></span>
  </div>
</div>

<div class="box">
  <div>
<pre class="brush:php;toolbar:false">.box {
  display: flex;
  margin: 5px;
}

.box > div {
  height: 50px;
  width: 100%;
  background: red;
  grid-template-columns: 200px 1fr;
  grid-template-rows: 1fr;
  grid-gap: 20px;
}

span {
  border: 2px solid green;
}

In the first box, the display property for the nested divs is not explicitly set. As a result, the default blockified display will be applied. In contrast, in the second box, the display is set to inline-grid, causing the inner divs to behave as a grid element. This is evident from the green borders around the spans, which align themselves accordingly.