[html] How to vertically align text inside a flexbox?

I would like to use flexbox to vertically align some content inside an <li> but not having great success.

I've checked online and many of the tutorials actually use a wrapper div which gets the align-items:center from the flex settings on the parent, but I'm wondering is it possible to cut out this additional element?

I've opted to use flexbox in this instance as the list item height will be a dynamic %.

* {_x000D_
  padding: 0;_x000D_
  margin: 0;_x000D_
}_x000D_
_x000D_
html,_x000D_
body {_x000D_
  height: 100%;_x000D_
}_x000D_
_x000D_
ul {_x000D_
  height: 100%;_x000D_
}_x000D_
_x000D_
li {_x000D_
  display: flex;_x000D_
  justify-content: center;_x000D_
  align-self: center;_x000D_
  background: silver;_x000D_
  width: 100%;_x000D_
  height: 20%;_x000D_
}

<ul>_x000D_
  <li>This is the text</li>_x000D_
</ul>

RESULT

HTML

<ul class="list">
  <li>This is the text</li>
  <li>This is another text</li>
  <li>This is another another text</li>
</ul>

Use align-items instead of align-self and I also added flex-direction to column.

CSS

* {
  padding: 0;
  margin: 0;
  box-sizing: border-box;
}

html,
body {
  height: 100%;
}

.list {
  display: flex;
  justify-content: center;
  flex-direction: column;  /* <--- I added this */
  align-items: center;   /* <--- Change here */
  height: 100px;
  width: 100%;
  background: silver;
}

.list li {  
  background: gold;
  height: 20%; 
}

Set the display in li as flex and set align-items to center.

li {
  display: flex;

  /* Align items vertically */
  align-items: center;

  /* Align items horizontally */
  justify-content: center;

}

I, personally, would also target pseudo elements and use border-box (Universal selector * and pseudo elements)

*,
*::before,
*::after {
  padding: 0;
  margin: 0;
  box-sizing: border-box;
}
  

The best move is to just nest a flexbox inside of a flexbox. All you have to do is give the child align-items: center. This will vertically align the text inside of its parent.

// Assuming a horizontally centered row of items for the parent but it doesn't have to be
.parent {
  align-items: center;
  display: flex;
  justify-content: center;
}

.child {
  display: flex;
  align-items: center;
}

It's depend on your li height just call one more thing line height

* {
  padding: 0;
  margin: 0;
}

html,
body {
  height: 100%;
}

ul {
  height: 100%;
}

li {
  display: flex;
  justify-content: center;
  align-self: center;
  background: silver;
  width: 100%;
  height:50px;line-height:50px;
}

<ul>
  <li>This is the text</li>
</ul>

Using display: flex you can control the vertical alignment of HTML elements.

.box {_x000D_
  height: 100px;_x000D_
  display: flex;_x000D_
  align-items: center; /* Vertical */_x000D_
  justify-content: center; /* Horizontal */_x000D_
  border:2px solid black;_x000D_
}_x000D_
_x000D_
.box div {_x000D_
  width: 100px;_x000D_
  height: 20px;_x000D_
  border:1px solid;_x000D_
}

<div class="box">_x000D_
  <div>Hello</div>_x000D_
  <p>World</p>_x000D_
</div>

You could change the ul and li displays to table and table-cell. Then, vertical-align would work for you:

ul {
    height: 20%;
    width: 100%;
    display: table;
}

li {
    display: table-cell;
    text-align: center;
    vertical-align: middle;
    background: silver;
    width: 100%; 
}

http://codepen.io/anon/pen/pckvK

The most voted answer is for solving this specific problem posted by OP, where the content (text) was being wrapped inside an inline-block element. Some cases may be about centering a normal element vertically inside a container, which also applied in my case, so for that all you need is:

align-self: center;

Instead of using align-self: center use align-items: center.

There's no need to change flex-direction or use text-align.

Here's your code, with one adjustment, to make it all work:

ul {
  height: 100%;
}

li {
  display: flex;
  justify-content: center;
  /* align-self: center;    <---- REMOVE */
  align-items: center;   /* <---- NEW    */
  background: silver;
  width: 100%;
  height: 20%; 
}

The align-self property applies to flex items. Except your li is not a flex item because its parent – the ul – does not have display: flex or display: inline-flex applied.

Therefore, the ul is not a flex container, the li is not a flex item, and align-self has no effect.

The align-items property is similar to align-self, except it applies to flex containers.

Since the li is a flex container, align-items can be used to vertically center the child elements.

* {_x000D_
  padding: 0;_x000D_
  margin: 0;_x000D_
}_x000D_
html, body {_x000D_
  height: 100%;_x000D_
}_x000D_
ul {_x000D_
  height: 100%;_x000D_
}_x000D_
li {_x000D_
  display: flex;_x000D_
  justify-content: center;_x000D_
  /* align-self: center; */_x000D_
  align-items: center;_x000D_
  background: silver;_x000D_
  width: 100%;_x000D_
  height: 20%;_x000D_
}

<ul>_x000D_
  <li>This is the text</li>_x000D_
</ul>

codepen demo

Technically, here's how align-items and align-self work...

The align-items property (on the container) sets the default value of align-self (on the items). Therefore, align-items: center means all flex items will be set to align-self: center.

But you can override this default by adjusting the align-self on individual items.

For example, you may want equal height columns, so the container is set to align-items: stretch. However, one item must be pinned to the top, so it is set to align-self: flex-start.

example

How is the text a flex item?

Some people may be wondering how a run of text...

<li>This is the text</li>

is a child element of the li.

The reason is that text that is not explicitly wrapped by an inline-level element is algorithmically wrapped by an inline box. This makes it an anonymous inline element and child of the parent.

From the CSS spec:

9.2.2.1 Anonymous inline boxes

Any text that is directly contained inside a block container element must be treated as an anonymous inline element.

The flexbox specification provides for similar behavior.

4. Flex Items

Each in-flow child of a flex container becomes a flex item, and each contiguous run of text that is directly contained inside a flex container is wrapped in an anonymous flex item.

Hence, the text in the li is a flex item.