digitalapps

This plugins detects all of the styles queued via wp_enqueue_style. Contents of each css file are copied and stored in a single css file. This file is loaded on the frontend. The plugin wp_dequeue_style and wp_deregister_style all other css files. The result is your website only makes one single http request to load css styling. Bonus feature the contents of the css file are minified.
Simply flip the switch and the plugin will do the rest.
NOTE: I have only tested this plugin on my own sites running the AdSense Theme. If you encounter a problem with this plugin please let me know. I will be able to help you.

WP CSS Merge

This plugins detects all of the styles queued via wp_enqueue_style. Contents of each css file are copied and stored in a single css file.

sh1zen

Improve Your WordPress Performance and SEO with WP-Optimizer (WPOPT) – Contains the most requested features for maintaining WordPress. Customizable in few easy steps to increase your website performances for an enhanced and safer user experience.
WHY USING WP Optimizer?
<ul>
<li>All In One: WPOPT support: image optimization, media clean-up, database optimization and backup, WordPress updates manager, Server info, Server configuration manager, WordPress performances enhancer, caching system and HTML – JavaScript – CSS minifier.</li>
<li>Modules Oriented: WPOPT is divided in modules, so you can disable not necessary one to reduce memory and CPU usage.</li>
<li>Easy to use: WPOPT was designed to be intuitive, allowing also non experts to be able to make that changes to have a great website.</li>
<li>Performances: WPOPT is built to speed up your site, every single module is optimized to ensure the best performance.</li>
<li>No limits: WPOPT has no limits, and could run in background</li>
<li>Multisite support.</li>
<li>Privacy: WPOPT does not collect nor send any data. Furthermore, all optimization actions run on your server, so that your stuff will remain yours.</li>
<li>No subscription email is asked or required.</li>
</ul>
BENEFITS
<ul>
<li>Improvements in search engine result page rankings.</li>
<li>At least 10x site performance improvements (Grade A in <a href="https://www.webpagetest.org/" rel="nofollow ugc">WebPagetest</a> or significant <a href="https://developers.google.com/speed/pagespeed/insights/" rel="nofollow ugc">Google Page Speed</a> improvements) when fully configured.</li>
<li>Reduced page load time: increased visitor time on site and number of viewed pages.</li>
<li>Improved web server performance: sustain high traffic periods.</li>
<li>Up to 80% bandwidth savings when images are optimized and HTML, CSS and JavaScript are minified.</li>
<li>Storage saver, optimized images required less disk space.</li>
</ul>
FEATURES
<ul>
<li>
Activity Log:
<ul>
<li>A useful WordPress activity log for users, posts and terms</li>
<li>Monito also bad access attempts like xss (cross-site-scripting) and sql injection </li>
<li>Supports custom rule monitoring</li>
</ul>
</li>
<li>
Cache: an advanced caching system to ensure best speed performance, with the lowest space used.
<ul>
<li>Object Caching: supports Memcached and Redis PHP extensions</li>
<li>WordPress Query Caching</li>
<li>Database Caching</li>
<li>Static page Caching</li>
</ul>
</li>
<li>
Database:
<ul>
<li>Backup, optimize, delete database tables</li>
<li>Clean up junk contents of WordPress leftovers items.</li>
</ul>
</li>
<li>
Media:
<ul>
<li>Image optimization and conversion supporting latest webp format </li>
<li>Media leftovers clean up tool</li>
<li>Auto image optimization in background</li>
<li>Runs in background, supporting also server with limited php execution time</li>
</ul>
</li>
<li>
Server Info:
<ul>
<li>Detailed useful information about your server, database, php and WordPress installation.</li>
</ul>
</li>
<li>
WP Optimizer:
<ul>
<li>WordPress Cron improver</li>
<li>Server htaccess enhancements</li>
<li>Server ongoing scripts compression (gzip, brotli)</li>
<li>Full control over Browser caching lifetime</li>
</ul>
</li>
<li>
WP Updates:
<ul>
<li>Get full controls over WordPress updates.</li>
</ul>
</li>
<li>
WP Security:
<ul>
<li>Offers an easy way to set up some basic security enhancements.</li>
<li>Soon will be available also blocking some specific attack patterns</li>
</ul>
</li>
<li>
WP Mail:
<ul>
<li>Mail Logging</li>
<li>Configure external smtp server</li>
</ul>
</li>
<li>
WP Customizer:
<ul>
<li>Prevent access to WordPress dashboard for non admins </li>
<li>Hide Admin Bar</li>
<li>Disable Block Editor</li>
<li>Disable Block Theme</li>
<li>Disable comments</li>
<li>Disable QuickPress, WordPress Blog and Welcome Panel</li>
<li>Fast category list filter in your editor</li>
<li>Disable WordPress sitemap, short-link generator, self-ping and many other features</li>
</ul>
</li>
<li>
Minify:
<ul>
<li>HTML, JavaScript and CSS optimization on the fly.</li>
</ul>
</li>
</ul>
DONATIONS
This plugin is free and always will be, but if you are feeling generous and want to show your support, you can buy me a 
beer or coffee <a href="https://www.paypal.com/donate/?business=dev.sh1zen%40outlook.it&item_name=Thank+you+in+advanced+for+the+kind+donations.+You+will+sustain+me+developing+WP-Optimizer.&currency_code=EUR" rel="nofollow ugc">here</a>, I will really appreciate it.

WP Optimizer

Optimize your website performances - Image compression, scripts minification, caching, database cleaner, server enhancements, activity log and more.

WP CSS Merge vs WP Optimizer