WP Rocket | Simple LoadCSS Preloader

Description

Simple high performance plugin to enhance WP Rocket’s css output to use the loadCSS preload polyfill.
This will ensure any css being loaded via the page output is deferred, and utilizing a preload [rel] attribute.
Note: This will not affect admin pages. It’s designed only to process front-end pages.

It is recommended to enable the WP Rocket setting for “Optimize CSS”, which will provide your pages with inline Critical-CSS.
That way an unstyled flash is not seen on page load (if properly configured of course).

This plugin will boost your Lighthouse and PageSpeed Insight scores.

Plugin Mission

We firmly believe that WP Rocket should implement this as a feature of their plugin.
If that takes place, we will update this plugin to mark it as deprecated.

Requirements:

• If you intend for logged-in users to see the effect, you must enable WP-Rocket’s setting called “caching for Logged-In Users”
• This plugin relies on having loadCSS present. It comes with it built in.
• • Alternatively, you can run the plugin without WP-Rocket, despite it’s intended purpose. (>^.^)>

Features:

• FilamentGroup’s LoadCSS(v2.0.1) inline injector
  (optional – see settings page next to WP Rocket), triggered via wp_head
• High performance Regular Expression approach to process WP Rocket’s (php’s) output buffer, to replace stylesheets with the appropriate loadCSS syntax
• Option to enable the buffer processor when you don’t have WP Rocket installed.
  ** This will respect AMP pages, and Yoast Sitemap output (by not executing). No other considerations have been implemented.

No fluff. Just a robust loadCSS implementation.

You can see how it works, & measure the performance, with this(via repl.it): Run the Plugin’s code
Just paste your own page’s url or html into the appropriate variable @ the top.

And you can test this plugin’s regex as well: WordPress.com html – links filtered by regex

Github link is here: Click

Last tested with:

• WP Rocket 3.1.x
• WordPress 4.9.x

Dependencies

• WP Rocket (optional via settings)
• file_get_contents() php function (if included loadCSS lib is used via options — default = yes)