bootstrap/docs/components/responsive-embed.md

layout	title
page	Responsive embed

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.

{% example html %}

{% endexample %}

Aspect ratios can be customized. There are two available in Bootstrap, 16x9 and 4x3 (two of the most common for video).

{% highlight html %}

{% endhighlight %}