BenJD

This WordPress plugin allows you to use responsive frames in your posts, pages or templates. Implemented via shortcode our responsive iFrames are simple and easy to use. Make sure your iFrames display correctly and adapt to different screen sizes and orientations.
Adding an iFrame to WordPress
Adding a responsive iFrame is simple. A small amount of shortcode is all that is required. The shortcode can be added to a post, a page or a wordpress template. Here is a simple example: [bjd-responsive-iframe src=”https://www.youtube.com/embed/UZr75lLiE6k”] This will create a responsive iframe for a youtube video. the ‘src’ attribute is required. Other optional attributes are also available.
 Attribute 
 Description 
 Example
 src 
 The source url for the iframe. 
 <iframe loading="lazy" class="youtube-player" width="640" height="360" src="https://www.youtube.com/embed/UZr75lLiE6k?version=3&rel=1&showsearch=0&showinfo=1&iv_load_policy=1&fs=1&hl=en-US&autohide=2&wmode=transparent" allowfullscreen="true" style="border:0;" sandbox="allow-scripts allow-same-origin allow-popups allow-presentation allow-popups-to-escape-sandbox"></iframe>
 id 
 Sets an id attribute for the iframe 
 youtubeVideo
 name 
 Sets a name attribute for the iframe 
 Example
 width 
 Sets the width attribute for the iframe 
 420
 height 
 Sets the height attribute for the iframe 
 300
 frameborder 
 Sets the frameborder attribute for the iframe 
 0
 scrolling 
 Sets the scrolling attribute for the iframe 
 yes OR no
 marginheight 
 Sets the marginheight attribute for the iframe 
 0
 marginwidth 
 Sets the marginwidth attribute for the iframe 
 0
Here is a more complicated example: [bjd-responsive-iframe src=”https://www.youtube.com/embed/UZr75lLiE6k” id=”youtubeVid” name=”youtubeVid” width=”560″ height=”315″ frameborder=”0″ scrolling=”no” marginheight=”0″ marginwidth=”0″ ]
Demo
A demonstration for the plugin working on wordpress 3 can be found here ( http://www.bj-dehaan-solutions.com.au/demos/wordpress3/responsive-iframe-demo/ ). 
A demonstration for the plugin working on wordpress 4 can be found here ( http://www.bj-dehaan-solutions.com.au/demos/wordpress4/responsive-iframe-demo/ ).

BJD Responsive iFrame

Palasthotel

greatestview

ATTENTION for WP Version 5+: This plugin does not work with Gutenberg (no problems with Classic Editor plugin though)! Gutenberg brings its own CSS for responsive oEmbed elements, so this plugin would double that and create strange effects.
This plugin uses some minimal CSS rules and a wrapping HTML element to maintain the aspect ratio of oEmbed elements with fixed aspect ratio (e. g. YouTube, Vimeo or Soundcloud).
Unlike other plugins, this plugin does not use any JavaScript!
The aspect ratio is calculated from the (iframe, object or embed) HTML tag width and height attributes. An aspect ratio will only be applied, if both width AND height attributes are given by the oEmbed element and if there is no data-secret attribut set (because those are handled via wp-embed.js). Some oEmbeds have no width or height attributes set, because they calculate their dimension via JavaScript. In those cases this plugin has no effect.
You can find a <a href="https://codex.wordpress.org/Embeds#Okay.2C_So_What_Sites_Can_I_Embed_From.3F" rel="nofollow ugc">list of all oEmbed sites supported by WordPress here</a>.

Responsive oEmbed

Exactly what i'm looking for.

Keep up the good work.

Great Plugin

Makes oEmbed elements with fixed aspect ratio (like YouTube, Vimeo or SoundCloud) scale responsively.

BJD Responsive iFrame vs Responsive oEmbed