This plugin hasn’t been tested with the latest 3 major releases of WordPress. It may no longer be maintained or supported and may have compatibility issues when used with more recent versions of WordPress.

CSS Optimizer – Remove Unused CSS


«Remove Unused CSS» is frequently flagged in Google’s PageSpeed Insights. Indeed, most scenario, around 70% – 80% of a page’s CSS codes are redundant, and can be removed without affecting the overall visual. This happens mainly because WordPress themes and plugins are created as generic solutions that includes a bunch of features that may or may not be used on a particular page.

Example: A theme may come with a bunch of features such as slider, carousel, animation and etc, but your home page may use only the slider feature and your about page may use only the carousel feature. However, for practical reason, it’s virtually impossible to selectively include only the required CSS rules for the features that were enabled on a particular page.

This is where the CSS Optimizer becomes useful. The plugin make calls to ZippiSite’s CSS Optimizer API to find the required CSS rules on a particular page, and remove the ones that are not needed.


  • Remove Unused CSS to pass Google PageSpeed Insights (Core Web Vitals)
  • Settings page, the only place you need to configure.


Is the CSS Optimizer API free to use?

It’s free to use with a quota of 150 API hits per months. Note that API hits does not equals page views. In our tests on real world websites, 150 API calls is able to serve approximately 1,000 monthly page views. In other words, the Free Plan should suffice for small websites.

If you require more API quota, paid plans are available, starting from as cheap as $3 for 800 monthly API calls – approximately 5,300 monthly page views.

What happens if there are styling issues after using this plugin?

We provide free support for all plans – even free plans. We’ll reply within 12 hours for paid plans, and within 24h for free plan.

What this plugin really does? Will it add extra burden to my server?

What this plugin does is to make calls to our API hosted on our server. The real heavy-lifting is done on our server, so you don’t need to worry that the plugin will require extra resources.


3. März 2023
The plugin simply catastrophically eats up space on the hosting.The site is 5.9 gigabytes. Of these, 3.9 gigabytes is occupied by the plugin cache in the wp-content folder.It’s not an optimizer plugin, it’s a pest plugin.
7. Juni 2022
After installing plugin, my site is completely broken, had to restore it with beckup.
10. November 2021
My website has a lot of unused CSS, by using this CSS optimizer. Mine CSS size decreased around 90%. Users-Friendly with a good design.
10. November 2021
This plugin has drastically helped my site! Before using the plugin, Google’s PageSpeed Insights keeps flagging my site with «Reduce Unused CSS» and «Eliminate render-blocking resources». What more can you ask for a free plugin?
Read all 6 reviews

Contributors & Developers

“CSS Optimizer – Remove Unused CSS” is open source software. The following people have contributed to this plugin.




  • Integrates with W3 Total Cache
  • Fix bug in job queue handling
  • Add warning in case of high amount of failed API calls


  • Integrates with WP-Optimize
  • Fix bug where relative path is being incorrectly processed
  • Fix compatibiliy issue with Autopimize
  • Improve admin dashboard notification
  • Add FAQ section


  • Integrats with SG Optimizer.
  • Improved compatibility.
  • Minor bug fixes


  • Integrates with WP Fastest Cache and WP Rocket. More integration coming soon!
  • Improvements in the general workflow.
  • Minor bug fixes.


  • Remove dependency on Auoptimize. The plugin can now work with or without Autoptimize.


  • Add Job Queue for easier management.


  • Add support for generating Critical CSS.


  • First version. More updates coming soon!