Autoptimize

Autoptimize is a very popular speed optimization plugin developed by Frank Goossens and available for free from the official WordPress repository. Can you improve your page load times with this plugin? Yes, you can.

The main three functions of this plugin are:

• minification and concatenation of CSS files
• minification and concatenation of Javascript
• minification of HTML code

The minification process is basically reducing the amount code to a minimum, without impacting its functionality. It involves, for example, deleting redundant (e.g. ";" at the end of CSS declarations) or useless character (e.g. multiple spaces or comments). Reducing the number of characters reduces the file size, and that is exactly the point of minification.

The concatenation process may sound complicated, but it is simply merging multiple CSS or Javascript files into a single .css or .js file. While in the HTTP/2 revision of the HTTP protocol multiple concurrent downloads are possible and some people think that nowadays concatenation does not make sense, based on my personal experience I think that a single 100 kB CSS file will load a little faster than 5 separate 20 kB files. Your mileage may vary, but please remember that larger files can achieve a higher GZIP compression rate and you should use GZIP compression on your server anyway, unless you use Brotli.

Autoptimize offers also a few other functions, but personally I am not a big fan of them. I haven't had good experiences with the lazy load function. The plugin can also optimize the delivery of Google web fonts. However, I think that hosting web fonts locally on your server is a much better solution. Autoptimize does not generate HTML cache, so it is not a replacement for caching plugins. It does create CSS and JS cache files, but it is not page cache.

As far as the core functions of minification and concatenation are concerned, I'd say that Autoptimize does a fantastic job and I have installed this plugin on all of my sites. Yes, some caching plugins, e.g. WP Rocket or Swift Performance, also offer the same functionality, but according to my tests, Autoptimize does a slightly better job. Hereby, I would like to thank Frank Goossens for creating this great plugin and offering it for free in the WordPress repository.