patrickpelayo

A Responsive Iframe that will resize itself to its parent element.
<h4>Instructions</h4>
<h4>Install</h4>
The plugin manager is located on the administration page. From the administration page in the left side bar click Plugins. From the top of the page click add new.
Install the plugin thru the plugin manager, or upload it as a zip file into the plugin manager.
<h4>Use</h4>
<ul>
<li>
Apply responsive iframe 
Create a post like you normally would and then click the + icon displayed to Add block. Find Responsive iframes and click it. 
By default your current website will be displayed in the iframe.
</li>
<li>
Block Settings 
Site Address – The url address of the website you want to iframe 
Width – This represents the actual width you want to display from the iframed website. 
Height – This represents the actual height you want to display from the iframed website. 
Scrollbar – Displays a scroll bar if the height,and width are smaller than the iframe website. 
Border – Dislays a default border around the iframe element. 
Scale – This will change the max-width percentage of the iframe’s parent element, it will allow the element to be scaled by size. 
Additional CSS – Any additional CSS will be applied to the iframe’s parent element. Use this to provide some additional styling.
</li>
<li>
BreakPoints 
Available under advanced settings, and will let you specify the width of the site to display depending on the width of the device. 
Multiple breakpoints can be used. The lowest BreakPoint Width will take effect over any higher BreakPoint Widths when the screen device is below or at its BreakPoint Width. 
Example Breakpoint 1 250px, Breakpoint 2 350px. A device with a screen width of 250px will only trigger Breakpoint 1. ScreenWidth 251px, will only trigger BreakPoint 2. 
Name – The name you wish to give the breakpoint 
BreakPoint Width – At and below this width, this breakpoint is triggered. 
Site Width – This is the width of the website to display when the breakpoint is triggered
</li>
</ul>

Responsive iframe

Lets you place Iframes into your posts that will resize dynamically to maintain the same apperance.

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.

Responsive iframe vs Responsive oEmbed