How to center vertically and horizontally a div using Bootstrap?

Question

I have a problem with my CSS. I have a panel form in my index page and I want to move it in the middle of the page vertically and horizontally. But I don't know how to create a CSS for this.

Here's my sample code:

<div class="login_header"></div>

<div class="container" style="text-align: center;">
    <div class="col-md-6 col-md-offset-3">
        <div class="panel_form panel panel-default">
            <div class="panel-content">
                <h1>test</h1>
            </div>
            <div class="panel-footer">
                <p>test</p>
            </div>
        </div>
    </div>
</div>

<footer class="footer"></footer>

I have a CSS like this:

.login_header { min-height: 50px; background-color: #f5f5f5; }

.panel_form {
   /* I don't have an idea with this */
}

.footer { 
    position: absolute; 
    bottom: 0; 
    width: 100%;
    height: 50px;
    background-color: #f5f5f5;
}

I am not good enough in CSS that's why I need your help. That's all thanks.. :)

Answer 1

Bootstrap 4:

<div class=" h-100 d-flex justify-content-center align-items-center">
  <div>
      Items are Centered horizontally and vertically
  </div>
</div>

JsFiddle

Answer 2

Some of the other answers on this question use CSS hacks with tables and custom CSS classes. As the poster asked "How to center vertically and horizontally using Bootstrap", here is how to do that using only Bootstrap 4 utility classes:

<div class="d-flex justify-content-md-center align-items-center vh-100">
    <p>Your Content</p>
</div>

Something of note is that due to the styling on the parent div, when adding additional elements in the same div, they will appear beside the first one, rather than below it. To fix this, just add an additional div inside the parent to reset the styling.

<div class="d-flex justify-content-md-center align-items-center vh-100">
    <div>
        <p>Content 1</p>
        <p>Content 2</p>
    </div>
</div>

This does work with Bootstrap flex, I've found that it works best when placed inside a flex component like this, rather than wrapping the entire row.

<div class="container">
    <div class="row">
        <div class="col-md-6">
            <div class="d-flex justify-content-md-center align-items-center vh-100">
                 <p>Content 1</p>
            </div>
        </div>
        <div class="col-md-6">
            <div class="d-flex justify-content-md-center align-items-center vh-100">
                 <p>Content 2</p>
            </div>
        </div>
    </div>
</div>

Here is a breakdown of each class:

1. d-flex: Effectively display: flex, allows the div to grow or shrink depending on the amount of content.
2. justify-content-md-center: Justifies content in the center of the page, can also be replaced with justify-content-sm-center or justify-content-lg-center to change the breakpoint.
3. align-items-center: Centers the alignments of all items in a div.
4. vh-100: Sets the height of the div to 100vh, or 100 "vertical height". This ensures that the div is the correct height to allow for vertical alignment.