Embeds were released with WordPress 4.4. This is basically the magic that auto converts your YouTube videos, Tweets, and URLs into pretty previews while you are editing. However, this actually loads a JavaScript file (wp-embed.min.js) on every page of your website. If you don’t care about the auto converting preview (which we don’t), you can disable this across your site.
In the perfmatters plugin simply enable the “Disable Embeds” option.
