Is your Wordpress website running slow? That's unfortunately not common and it's one of Wordpress's curses. Being simple to use and having so many features means it's very complex at the back end and there's lots of little potential bugs that can cause your site to slow down. In saying that, there are a few basic things you can do to make sure your Wordpress site is running as fast as possible. I've listed them here in the order we at Crucial see as the most helpful:
Before you start, how to test your site: You should test your site before and after completing each step. The easiest way to do this is to use a site like GTMetrix, Google PageSpeed Insights or Pingdom Tools. These will give a detailed breakdown of how your site loads. Of the 3 I prefer Pingdom as it allows you to test from a server in Australia, which will give the most accurate and relevant results for our customers (off course if your clients are in the USA or Europe/Sweden using the appropriate server will give the best results in that situation).
You can also test your site a more manual way. Open your main/index page, then open every link on the front page at the same time (you can middle click/mouse wheel click to open automatically in a new tab) and see how long all the pages take to load. I personally prefer this way, as it reflects more accurately on the experiences your visitors may have.
1 - Updating Wordpress, Plugins and Themes
Wordpress updates regularly contain updates to not only speed your website up but also plug security holes. It's a good idea to make sure that Wordpress, it's plugins and folders are all kept up to date. Click here for a guide on doing this.
2 - Install WP Super Cache
Wordpress is made up of lots of little programs (.php files) that collectively work to generate a page each time someone visits your site. A caching program captures that page, so that rather than 100 visitors each having the page generated individually, the page is generated once, saved on the server, and then served to each visitor. This can often have a night and day effect on your site's speed:
While there are multiple caching plugins for Wordpress (W3 Total Cache, Jetpack, etc) we find that a specific configuration of Super Cache works best on Crucial's servers.
NOTE: If you're using Woo Commerce or another shopping cart plugin we recommend being careful with caching. In this case, it's better to, instead of Super Cache, use a default installation of the W3 Total Cache plugin then click here and follow the steps on the Woo Commerce guide to making sure the plugin is configured correctly for your site.
3 - Updating Wordpress Cron Job
Think of the Wordpress Cron as the 3rd level of caching. There are some PHP files that Wordpress needs to run on a regular basis. By default, it will only run these files when a user visits the site. There's a better way to do it. We can configure these PHP files to run every x amount of minutes, so when someone visits the site they have already run and the visitor doesn't have to wait for the site to load.
4 - Updating PHP Version
Updating PHP can, in many cases, be the easiest change to make and will give the largest improvement to speeding your Wordpress site up.
Note 1: When updating you must make sure to update one version at a time. Newer PHP versions remove obsolete functions from older versions. If your site uses those functions, updating will break the site and you will need to go back. Start by updating, for example, from 5.4 to 5.5. Go to your website. Test all the pages and functions to make sure everything works correctly. If it's fine, go to 5.6 and test the site again.
Note 2: PHP 7 is a big leap from the 5 series and provides up to a 50% speed boost and 50% reduced memory usage. It is also more secure than PHP 5. Further to this, it is actively being worked on meaning it will continue to receive speed and security updates. Some older sites may have compatibility problems with PHP 7, while 5.6 is far more compatible. We do recommend moving to 7 and if you have any incompatible themes/plugins you may want to look for alternates as PHP5 is due to stop receiving security updates within a few months and PHP7 will make sure your website is faster, safer and more future proof.