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Bootstrap 4 Beta is here!

Utilities

Bootstrap includes dozens of utilities—classes with a single purpose to reduce the frequency of highly repetitive declarations.

Responsive helpers

Responsive embeds

Allow browsers to determine video or slideshow dimensions based on the width of their containing block by creating an intrinsic ratio that will properly scale on any device.

Rules are directly applied to <iframe>, <embed>, <video>, and <object> elements; optionally use an explicit descendant class .embed-responsive-item when you want to match the styling for other attributes.

Pro-Tip! You don’t need to include frameborder="0" in your <iframe>s as we override that for you.

<div class="embed-responsive embed-responsive-16by9">
  <iframe class="embed-responsive-item" src="//www.youtube.com/embed/zpOULjyy-n8?rel=0" allowfullscreen></iframe>
</div>

Aspect ratios can be customized with modifier classes.

<!-- 21:9 aspect ratio -->
<div class="embed-responsive embed-responsive-21by9">
  <iframe class="embed-responsive-item" src="..."></iframe>
</div>

<!-- 16:9 aspect ratio -->
<div class="embed-responsive embed-responsive-16by9">
  <iframe class="embed-responsive-item" src="..."></iframe>
</div>

<!-- 4:3 aspect ratio -->
<div class="embed-responsive embed-responsive-4by3">
  <iframe class="embed-responsive-item" src="..."></iframe>
</div>

<!-- 1:1 aspect ratio -->
<div class="embed-responsive embed-responsive-1by1">
  <iframe class="embed-responsive-item" src="..."></iframe>
</div>

Responsive floats

These utility classes float an element to the left or right, or disable floating, based on the current viewport size using the CSS float property. !important is included to avoid specificity issues. These use the same viewport width breakpoints as the grid system.

Two similar non-responsive Sass mixins (float-left and float-right) are also available.

Float left on all viewport sizes

Float right on all viewport sizes

Don't float on all viewport sizes

Float left on viewports sized SM (small) or wider

Float left on viewports sized MD (medium) or wider

Float left on viewports sized LG (large) or wider

Float left on viewports sized XL (extra-large) or wider

<div class="float-left">Float left on all viewport sizes</div><br>
<div class="float-right">Float right on all viewport sizes</div><br>
<div class="float-none">Don't float on all viewport sizes</div><br>

<div class="float-sm-left">Float left on viewports sized SM (small) or wider</div><br>
<div class="float-md-left">Float left on viewports sized MD (medium) or wider</div><br>
<div class="float-lg-left">Float left on viewports sized LG (large) or wider</div><br>
<div class="float-xl-left">Float left on viewports sized XL (extra-large) or wider</div><br>
// Related simple non-responsive mixins
.element {
  @include float-left;
}
.another-element {
  @include float-right;
}