Dustin Lammiman

This plugin takes advantage of WordPress’ built in <a href="https://codex.wordpress.org/Embeds" rel="nofollow ugc">oEmbed functionality</a> to make it easy to insert responsive videos into your site or blog. Just copy the URL of the video you want to embed and paste it into the WordPress editor. This plugin will maintain the default aspect ratio of the video at any page size.
This plugin has been tested as working with the following video sites:
<ul>
<li>
YouTube
</li>
<li>
Vimeo
</li>
<li>
blip.tv
</li>
<li>
Flickr (videos)
</li>
<li>
DailyMotion
</li>
<li>
Hulu
</li>
<li>
WordPress.tv
</li>
<li>
FunnyOrDie.com (WordPress 3.0+)
</li>
<li>
Revision3
</li>
</ul>
View the source <a href="https://github.com/nosecreek/Responsive-Video-for-WordPress" rel="nofollow ugc">on GitHub</a>.

Responsive Video for WordPress

Using a responsive WordPress theme? Make your videos responsive too! Just activate this plugin, and your videos will be instantly responsive!

jeroenooms

This WordPress plugin makes embedded media responsive.
To embed a video or another object into a WordPress post or page, place its URL into the content area. 
Make sure the URL is on its own line and not hyperlinked (clickable when viewing the post).
WordPress will automatically turn the URL into a YouTube embed and provide a live preview in the visual editor. 
Read more information about supported platforms and alternative implementations at <a href="https://codex.wordpress.org/Embeds" rel="nofollow ugc">WordPress.org</a>.
<h4>Supported platforms with this Responsive Media plugin</h4>
After installing this plugin, the following media will be responsive automaticly even on earlier published posts and pages. The version numbers show since when these oEmbedded media are supported by WordPress.
<ul>
<li>Flickr (2.9.0) [1]</li>
<li>Kickstarter (4.2.0)</li>
<li>Slideshare (3.5.0)</li>
<li>Soundcloud (3.5.0)</li>
<li>Speakerdeck (4.4.0)</li>
<li>TED Talks (4.0.0)</li>
<li>Videopress (4.4.0)</li>
<li>Vimeo (2.9.0)</li>
<li>Vine (4.1.0)</li>
<li>Youtube (2.9.0) [2]</li>
<li>WordPress.tv (2.9.0)</li>
</ul>
Responsive support without plugin:
<ul>
<li>Meetup (3.9.0)</li>
</ul>
[1] Flic.kr domain since 3.6.0 
[2] Youtu.be domain since 3.0.0, Youtube playlists since 4.0.0

Responsive Media

Wordpress plugin for responsive embedded media (oEmbed) like Youtube, Vimeo, Flickr, Kickstarter, Slideshare, Soundcloud, Speakerdeck, TED & Vine.

Responsive Video for WordPress vs Responsive Media