min-width and max-width with the same value?

Question

In the past, I saw the next css and I was thinking if there is some actual difference between

min-width: 90px;
max-width: 90px;

and

width: 90px;

Answer 1

using width will simply specify fixed width over the element without paying attention to its content (so you can have overflow) :

div {
  width: 80px;
  border:2px solid red;
}

<div>
  <img src="https://lorempixel.com/200/100/" />
</div>

Using max-width means that the element will have an upper bound for its width. So its width can be from 0 to max-width depending on its content.

div {
  max-width: 300px;
  border: 2px solid red;
}

.diff {
  display: inline-block;
}

<div>
  <!-- this i a block element so max-width prevent it from taking 100% width -->
  <img src="https://lorempixel.com/200/100/" />
</div>
<div class="diff">
  <!-- this i an inline-block element so max-width has no effect in this case cause the content is taking less than 300px  -->
  <img src="https://lorempixel.com/200/100/" />
</div>
<div>
  <!-- You have overflow because the element cannot have more than 300 of width -->
  <img src="https://lorempixel.com/400/100/" />
</div>

And min-width specify lower bound for width. So the width of the element will vary from min-width to ... (it will depend on other style).

div {
  min-width: 300px;
  border: 2px solid red;
}

.diff {
  display: inline-block;
  min-height:50px;
}

<div>
  <img src="https://lorempixel.com/200/100/" />
</div>
<div class="diff">
  
</div>
<div class="diff">
  <img src="https://lorempixel.com/200/100/" />
</div>
<div>
  <img src="https://lorempixel.com/400/100/" />
</div>

---

So if you specify min-width and max-width, you will set up a lower and upper bound and if both are equal it will be the same as simply specifing a width.

div {
  min-width: 300px;
  max-width: 300px;
  border: 2px solid red;
}

.diff {
  display: inline-block;
  min-height:50px;
}

<div>
  <img src="https://lorempixel.com/200/100/" />
</div>
<div class="diff">
  
</div>
<div class="diff">
  <img src="https://lorempixel.com/200/100/" />
</div>
<div>
  <img src="https://lorempixel.com/400/100/" />
</div>

Special Cases

In some particular cases, width will not give the same result as min-width/max-width like with Flexbox where we have the shrink feature that allow an element to shrink to fit its container

.box {
  width:200px;
  border:1px solid red;
  display:flex;
  margin:5px;
}
.box > div {
  border:2px solid;
  height:50px;
}

<div class="box">
  <div style="width:300px"></div>
</div>

<div class="box">
  <div style="min-width:300px;max-width:300px;"></div>
</div>

As you can see in the second case the element will not shrink because, unlike width, min-width will prevent this.

Another case is the use of resize property:

div {
  border: 2px solid;
  height: 50px;
  overflow: auto;
  resize: both;
}

<div style="width:300px"></div>

<div style="min-width:300px;max-width:300px;"></div>

As you can see, we can resize the element defined by width and not the one defined by min-width/max-width

---

We should also note that min-width/max-width is more powerful than width. Setting the 3 properties to different values will make min-width the winner

.box {
  border: 2px solid;
  height: 50px;
  width:100px;
  min-width:200px;
  max-width:150px;
}

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

This means that we can override a value set by width using min-width/max-width but not the opposite