[html] How to vertically center a container in Bootstrap?

The Flexible box way

Vertical alignment is now very simple by the use of Flexible box layout. Nowadays, this method is supported in a wide range of web browsers except Internet Explorer 8 & 9. Therefore we'd need to use some hacks/polyfills or different approaches for IE8/9.

In the following I'll show you how to do that in only 3 lines of text (regardless of old flexbox syntax).

Note: it's better to use an additional class instead of altering .jumbotron to achieve the vertical alignment. I'd use vertical-center class name for instance.

Example Here (A Mirror on jsbin).

<div class="jumbotron vertical-center"> <!-- 
                      ^--- Added class  -->
  <div class="container">
    ...
  </div>
</div>

.vertical-center {
  min-height: 100%;  /* Fallback for browsers do NOT support vh unit */
  min-height: 100vh; /* These two lines are counted as one :-)       */

  display: flex;
  align-items: center;
}

Important notes (Considered in the demo):

1. A percentage values of height or min-height properties is relative to the height of the parent element, therefore you should specify the height of the parent explicitly.

2. Vendor prefixed / old flexbox syntax omitted in the posted snippet due to brevity, but exist in the online example.

3. In some of old web browsers such as Firefox 9 ^{(in which I've tested)}, the flex container - .vertical-center in this case - won't take the available space inside the parent, therefore we need to specify the width property like: width: 100%.

4. Also in some of web browsers as mentioned above, the flex item - .container in this case - may not appear at the center horizontally. It seems the applied left/right margin of auto doesn't have any effect on the flex item.
   Therefore we need to align it by box-pack / justify-content.

For further details and/or vertical alignment of columns, you could refer to the topic below:

• vertical-align with Bootstrap 3

The traditional way for legacy web browsers

This is the old answer I wrote at the time I answered this question. This method has been discussed here and it's supposed to work in Internet Explorer 8 and 9 as well. I'll explain it in short:

In inline flow, an inline level element can be aligned vertically to the middle by vertical-align: middle declaration. Spec from W3C:

middle
Align the vertical midpoint of the box with the baseline of the parent box plus half the x-height of the parent.

In cases that the parent - .vertical-center element in this case - has an explicit height, by any chance if we could have a child element having the exact same height of the parent, we would be able to move the baseline of the parent to the midpoint of the full-height child and surprisingly make our desired in-flow child - the .container - aligned to the center vertically.

Getting all together

That being said, we could create a full-height element within the .vertical-center by ::before or ::after pseudo elements and also change the default display type of it and the other child, the .container to inline-block.

Then use vertical-align: middle; to align the inline elements vertically.

Here you go:

<div class="jumbotron vertical-center">
  <div class="container">
    ...
  </div>
</div>

.vertical-center {
  height:100%;
  width:100%;

  text-align: center;  /* align the inline(-block) elements horizontally */
  font: 0/0 a;         /* remove the gap between inline(-block) elements */
}

.vertical-center:before {    /* create a full-height inline block pseudo=element */
  content: " ";
  display: inline-block;
  vertical-align: middle;    /* vertical alignment of the inline element */
  height: 100%;
}

.vertical-center > .container {
  max-width: 100%;

  display: inline-block;
  vertical-align: middle;  /* vertical alignment of the inline element */
                           /* reset the font property */
  font: 16px/1 "Helvetica Neue", Helvetica, Arial, sans-serif;
}

WORKING DEMO.

Also, to prevent unexpected issues in extra small screens, you can reset the height of the pseudo-element to auto or 0 or change its display type to none if needed so:

@media (max-width: 768px) {
  .vertical-center:before {
    height: auto;
    /* Or */
    display: none;
  }
}

UPDATED DEMO

And one more thing:

If there are footer/header sections around the container, it's better to position that elements properly (relative, absolute? up to you.) and add a higher z-index value (for assurance) to keep them always on the top of the others.