Scott (@scottsweb)

Fillet adds a new IFrame button to the toolbar in the WordPress visual editor. By using a <a href="https://codex.wordpress.org/Shortcode" rel="nofollow ugc">shortcode</a>, it allows for safer, responsive and future proof embeds.
The chosen width and height for an IFrame embed is converted into a ratio which is used to scale your embeds across different devices.
<a href="http://scott.ee/" title="WordPress web design Hampshire" rel="nofollow ugc">a plugin by Scott Evans</a>

fillet

Safely embed responsive IFrames in the WordPress text editor.

lencinhaus

force-frame is a <a href="https://wordpress.org/" rel="ugc">WordPress</a> plugin that allows you to force your WordPress website inside an iframe in another website, with cross-domain support.
<h4>Features</h4>
<ul>
<li>Redirect to parent site: when users access your website directly, they will be redirected to the parent site where your site is shown in an iframe.</li>
<li>Inject site’s URL into parent site’s URL: when users navigate between pages in your site, the URL they navigate to is injected in the parent site’s URL using the fragment or a GET parameter; if the parent site’s URL is then shared, the iframe will load the correct page of your site</li>
<li>Cross-domain support: it will work even if your site and the parent site are on different domains</li>
</ul>
Links: <a href="http://www.cubica.eu" rel="nofollow ugc">Author’s Site</a>
<h3>!!IMPORTANT!!</h3>
If you’re upgrading to version 1.2+ from a previous version, you will have to replace the iframe in the parent site with a script: please follow the instructions in the Force Frame settings page.

fillet vs Force Frame