Everyone knows that time is money. For example, restaurants with slow service don’t receive good reviews. Similarly, a slow website frustrates visitors (Neil Patel argues that 40% of website visitors will leave a website that takes more than 3 seconds to load). Other studies show that a fast website improves customer experience and increases conversion rates. Increases in speed improves your sales revenue. Recently, we tested different WordPress themes and plugins to determine how they affect website speed. Read on to discover our surprising WordPress speed testing results.

Test setup

We used our internal network and a local web server for the tests. While our WordPress speed tests may not represent real world results due to our controlled environment, the testing results are indicative of how different themes and plugins affect a website’s speed. The same websites on a live server will run slower.

We tested eight themes (seven of the most popular themes – including TwentyNineteen and a custom-made Bootstrap-based theme). We also tested each theme with four popular plugins installed (in addition to website with no plugins installed). We created a single page with several common page elements (headings, text, and images). For the Divi theme, we recreated the page using the Divi Builder. We cleared our browser cache after each theme and plugin activation test. In all, this resulted in 40 individual tests.

Testing results

Our testing results

On a fresh installation of WordPress with no plugins installed, the TwentyNineteen, Divi, and custom Bootstrap themes consistently ran slower than the other themes. We were surprised with the custom theme results because we specifically tailored this theme for speed (minified CSS and JavaScript, optimized images, etc). The Genesis theme performed the fastest. Touted as a generic theme specifically created for customization, the Genesis theme surprised us.

Adding plugins to the testing website affected some themes differently. The Contact Form 7 plugin slowed down all website tests (except for the Astra theme). The Classic Editor plugin did not seem to affect the website speed (which makes sense because the same WordPress developers created the Classic Editor). The other plugins had a minimal impact on page loading speed.

Some messed up

We were surprised that two themes (Sydney and Hestia) messed with our page content. They either didn’t display the content correctly or they just didn’t show the content. The Divi theme with the Divi Builder plugin added a tremendous amount of extra code to our web page. This bloat remained, even after removing the Divi theme and Divi Builder plugin. We had to manually edit the page code to remove the extra code. For typical WordPress users, having to manually edit page code is very time consuming and error prone.

Running these tests confirmed our suspicions that some themes and plugins impacted page loading times. When selecting themes and plugins for your WordPress website, pay attention to their effect on page speed. Ask yourself if you really need the functionality offered by the plugin. Also choose your theme wisely as picking the wrong theme will slow your website. Use our WordPress speed testing results as a guideline when setting up your website.

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