Keep the middle item centered when side items have different widths

Html Problem Overview

Imagine the following layout, where the dots represent the space between the boxes:

[Left box]......[Center box]......[Right box]

When I remove the right box, I like the center box to still be in the center, like so:

[Left box]......[Center box].................

The same goes for if I would remove the left box.

................[Center box].................

Now when the content within the center box gets longer, it will take up as much available space as needed while remaining centered. The left and right box will never shrink and thus when where is no space left the overflow:hidden and text-overflow: ellipsis will come in effect to break the content;

[Left box][Center boxxxxxxxxxxxxx][Right box]

All the above is my ideal situation, but I have no idea how to accomplish this effect. Because when I create a flex structure like so:

.parent {
    display : flex; // flex box
    justify-content : space-between; // horizontal alignment
    align-content   : center; // vertical alignment
}

If the left and right box would be exactly the same size, I get the desired effect. However when one of the two is from a different size the centered box is not truly centered anymore.

Is there anyone that can help me?

Update

A justify-self would be nice, this would be ideal:

.leftBox {
     justify-self : flex-start;
}

.rightBox {
    justify-self : flex-end;
}

Html Solutions

Solution 1 - Html

>If the left and right boxes would be exactly the same size, I get the desired effect. However when one of the two is a different size the centered box is not truly centered anymore. Is there anyone that can help me?

Here's a method using flexbox to center the middle item, regardless of the width of siblings.

Key features:

pure CSS
no absolute positioning
no JS/jQuery

Use nested flex containers and auto margins:

.container {
  display: flex;
}
.box {
  flex: 1;
  display: flex;
  justify-content: center;
}

.box:first-child > span { margin-right: auto; }

.box:last-child  > span { margin-left: auto;  }

/* non-essential */
.box {
  align-items: center;
  border: 1px solid #ccc;
  background-color: lightgreen;
  height: 40px;
}
p {
  text-align: center;
  margin: 5px 0 0 0;
}

<div class="container">
  <div class="box"><span>short text</span></div>
  <div class="box"><span>centered text</span></div>
  <div class="box"><span>loooooooooooooooong text</span></div>
</div>
<p>&#8593;<br>true center</p>

Here's how it works:

The top-level div (.container) is a flex container.
Each child div (.box) is now a flex item.
Each .box item is given flex: 1 in order to distribute container space equally (more details).
Now the items are consuming all space in the row and are equal width.
Make each item a (nested) flex container and add justify-content: center.
Now each span element is a centered flex item.
Use flex auto margins to shift the outer spans left and right.

You could also forgo justify-content and use auto margins exclusively.

But justify-content can work here because auto margins always have priority.

> 8.1. Aligning with auto > margins > > Prior to alignment via justify-content and align-self, any > positive free space is distributed to auto margins in that dimension.

Solution 2 - Html

Use three flex items in the container
Set flex: 1 to the first and last ones. This makes them grow equally to fill the available space left by the middle one.
Thus, the middle one will tend to be centered.
However, if the first or last item has a wide content, that flex item will also grow due to the new min-width: auto initial value.

Note Chrome doesn't seem to implement this properly. However, you can set min-width to -webkit-max-content or -webkit-min-content and it will work too.

Only in that case the middle element will be pushed out of the center.

.outer-wrapper {
  display: flex;
}
.item {
  background: lime;
  margin: 5px;
}
.left.inner-wrapper, .right.inner-wrapper {
  flex: 1;
  display: flex;
  min-width: -webkit-min-content; /* Workaround to Chrome bug */
}
.right.inner-wrapper {
  justify-content: flex-end;
}
.animate {
  animation: anim 5s infinite alternate;
}
@keyframes anim {
  from { min-width: 0 }
  to { min-width: 100vw; }
}

<div class="outer-wrapper">
  <div class="left inner-wrapper">
    <div class="item animate">Left</div>
  </div>
  <div class="center inner-wrapper">
    <div class="item">Center</div>
  </div>
  <div class="right inner-wrapper">
    <div class="item">Right</div>
  </div>
</div>
<!-- Analogous to above --> <div class="outer-wrapper"><div class="left inner-wrapper"><div class="item">Left</div></div><div class="center inner-wrapper"><div class="item animate">Center</div></div><div class="right inner-wrapper"><div class="item">Right</div></div></div><div class="outer-wrapper"><div class="left inner-wrapper"><div class="item">Left</div></div><div class="center inner-wrapper"><div class="item">Center</div></div><div class="right inner-wrapper"><div class="item animate">Right</div></div></div>

Solution 3 - Html

The key is to use flex-basis. Then the solution is simple as:

.parent {
    display: flex;
    justify-content: space-between;
}

.left, .right {
   flex-grow: 1;
   flex-basis: 0;
}

CodePen is available here.

Solution 4 - Html

Here's an answer that uses grid instead of flexbox. This solution doesn't require extra grandchild elements in the HTML like the accepted answer does. And it works correctly even when the content on one side gets long enough to overflow into the center, unlike the grid answer from 2019.

The one thing this solution doesn't do is show an ellipsis or hide the extra content in the center box, as described in the question.

section {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
}

section > *:last-child {
  white-space: nowrap;
  text-align: right;
}

/* not essential; just for demo purposes */
section {
  background-color: #eee;
  font-family: helvetica, arial;
  font-size: 10pt;
  padding: 4px;
}

section > * {
  border: 1px solid #bbb;
  padding: 2px;
}

<section>
  <div>left</div>
  <div>center</div>
  <div>right side is longer</div>
</section>

<section>
  <div>left</div>
  <div>center</div>
  <div>right side is much, much longer</div>
</section>

<section>
  <div>left</div>
  <div>center</div>
  <div>right side is much, much longer, super long in fact</div>
</section>

Solution 5 - Html

Instead of defaulting to using flexbox, using grid solves it in 2 lines of CSS without additional markup inside the top level children.

HTML:

<header class="header">
  <div class="left">variable content</div>
  <div class="middle">variable content</div>
  <div class="right">variable content which happens to be very long</div>
</header>

CSS:

.header {
  display: grid;
  grid-template-columns: [first] 20% auto [last] 20%;
}
.middle {
  /* use either */
  margin: 0 auto;
  /* or */
  text-align: center;
}

Flexbox rocks but shouldn't be the answer for everything. In this case grid is clearly the cleanest option.

Even made a codepen for your testing pleasure: https://codepen.io/anon/pen/mooQOV

Solution 6 - Html

You can do this like so:

.bar {
    display: flex;    
    background: #B0BEC5;
}
.l {
    width: 50%;
    flex-shrink: 1;
    display: flex;
}
.l-content {
    background: #9C27B0;
}
.m { 
    flex-shrink: 0;
}
.m-content {    
    text-align: center;
    background: #2196F3;
}
.r {
    width: 50%;
    flex-shrink: 1;
    display: flex;
    flex-direction: row-reverse;
}
.r-content { 
    background: #E91E63;
}

<div class="bar">
    <div class="l">
        <div class="l-content">This is really long content.  More content.  So much content.</div>
    </div>
    <div class="m">
        <div class="m-content">This will always be in the center.</div>
    </div>
    <div class="r">
        <div class="r-content">This is short.</div>
    </div>
</div>

Solution 7 - Html

Here is another way to do it, using display: flex in the parents and childs:

.Layout{
    display: flex;
    justify-content: center;
}
.Left{
    display: flex;
    justify-content: flex-start;
    width: 100%;
}
.Right{
    display: flex;
    justify-content: flex-end;
    width: 100%;
}

<div class = 'Layout'>
    <div class = 'Left'>I'm on the left</div>
    <div class = 'Mid'>Centered</div>
    <div class = 'Right'>I'm on the right</div>
</div>

Solution 8 - Html

I wanted the exact result shown in the question, I combined answers from gamliela and Erik Martín Jordán and it works best for me.

.parent {
    display: flex;
    justify-content: space-between;
}

.left, .right {
   flex-grow: 1;
   flex-basis: 0;
}

.right {
   display: flex;
   justify-content: flex-end;
}

Solution 9 - Html

A slightly more robust grid solution looks like this:

.container { overflow: hidden; border-radius: 2px; padding: 4px; background: orange; display: grid; grid-template-columns: minmax(max-content, 1fr) auto minmax(max-content, 1fr); }

.item > div { display: inline-block; padding: 6px; border-radius: 2px; background: teal; }

.item:last-child > div { float: right; }

edit the text to test the layout

just click me and

edit

And here you can see it in Codepen: https://codepen.io/benshope2234/pen/qBmZJWN

Solution 10 - Html

you can also use this simple way to reach exact center alignment for middle element :

.container {
	display: flex;
    justify-content: space-between;
}

.container .sibling {
	display: flex;
	align-items: center;
    height: 50px;
    background-color: gray;
}

.container .sibling:first-child {
	width: 50%;
    display: flex;
    justify-content: space-between;
}

.container .sibling:last-child {
	justify-content: flex-end;
	width: 50%;
	box-sizing: border-box;
	padding-left: 100px; /* .center's width divided by 2 */
}

.container .sibling:last-child .content {
	text-align: right;
}

.container .sibling .center {
    height: 100%;
    width: 200px;
    background-color: lightgreen;
    transform: translateX(50%);
}

codepen: https://codepen.io/ErAz7/pen/mdeBKLG

Solution 11 - Html

Althought I might be late on this one, all those solutions seems complicated and may not work depending on the cases you're facing.

Very simply, just wrap the component you want to center with position : absolute, while letting the other two with justify-content : space-between, like so :