Is there any difference setting width: auto; and width: fit-content;?

Question

From what I know, setting width: fit-content; to the element simply means that the element width will take up the available space but never less than the min-content within the element. But, isn't the default width: auto; behaves the same as well?

Just wondering when should I use width: fit-content;?

Answer 1

width: auto is the default width for all elements, so the width will rely on display types (block, inline, etc.) to show respectively.

To make you understand better about width:auto, I put 2 code snippets below

Case 1: Using div with display: block as default

.container {
  border: 2px solid #ccc;
  padding: 10px;
  width: 20em;
}

.item {
  width: auto;
  background-color: lightblue;
  padding: 5px;
  margin-bottom: 1em;
}

<div class="container">
  <div class="item">Item</div>
  <div class="item">Item with more text in it.</div>
  <div class="item">Item with more text in it, hopefully it's lengthy enough for the demo</div>
</div>

Case 2: Using span with display: inline as default

.container {
  border: 2px solid #ccc;
  padding: 10px;
  width: 20em;
}

.item {
  width: auto;
  background-color: lightblue;
  padding: 5px;
  margin-bottom: 1em;
}

<div class="container">
  <span class="item">Item</span>
  <span class="item">Item with more text in it.</span>
  <span class="item">Item with more text in it, hopefully it's lengthy enough for the demo</span>
</div>

So basically, display: block will take up the whole width for element display, and display: inline and display: inline-block will align with content width. The next question is why we don't use display: inline or display: inline-block instead of width: fit-content?

Let's check the below code snippet for div with width: fit-content

.container {
  border: 2px solid #ccc;
  padding: 10px;
  width: 20em;
}

.item {
  width: fit-content;
  background-color: lightblue;
  padding: 5px;
  margin-bottom: 1em;
}

<div class="container">
  <div class="item">Item</div>
  <div class="item">Item with more text in it.</div>
  <div class="item">Item with more text in it, hopefully it's lengthy enough for the demo</div>
</div>

You can see that each content line has been shown with an individual color box, and it does not consume other lines' space

As your question

Just wondering when should I use width: fit-content;?

In my personal experience, I've been usually using width: fit-content; when I want to show tags with fit borders

Source

All my tags can be shown in different lines but borders will be displayed respectively by content, so width: fit-content is a good choice for me.

P/s: Actually, we can achieve this design in other ways like using a wrapper, using flexbox, etc. But I personally like width: fit-content because it's simpler. One thing I'd like to note is that this approach does not work well with Internet Explorer (check browser compatibility here)