Case Study – Influence of WordPress Plugins on Website Speed

WordPress plugins are small snippets of code which can be installed for better functionality and productive purposes. There are more than 50,000 plugins to provide the necessary aesthetic, SEO and other features. To install them you can directly use the WordPress dashboard or download from the main WordPress.org website.

There are pro and cons of using WordPress plugins. If they are not properly coded, it can cause security breach to your website. Also SQL injection of code is possible through some plugins. In many cases, use of a correct security plugin stops these insecure code execution.

The main issue with WordPress plugins is how they impact the speed of your site. As we know, Google has clearly stated that “page loading speed” is an important signal of ranking web pages. If your page loads more than 3 seconds, you are likely to loss 50% of your revenue. This is because visitors are more likely to leave the page and thus less ROI.

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To test this theory that some WordPress plugins slow down your website, I took a case-study on one of my websites.

Case 1: Initial Case without any WordPress Plugins

All the plugins were deactivated to test website speed.

I used a test page from the site to check the page speed performance results. I was astonished to find that after disabling all the plugins, my page loading time has reduced to 1.4s. The total page size was also reduced to 151KB and there were only 15 requests.

The PageSpeed Score was A(98%) and YSlow Score was A(92%). I tested the web page using GTMetrix page speed tool. The server location was Vancouver, Canada. The speed metric testing service used Chrome (Desktop) 75.0.3770.100, PageSpeed 1.15-gt1.2, YSlow 3.1.8 versions.

I tested the same page using Pingdom Testing Tool service. The web page was tested using London, UK, Europe location. My server was situated in United States. So the ping hop was large enough to check the page speed performance.

The test results showed load time of 1.61s, page size of 155.4KB and 19 requests. It gave a B(63) performance grade.

The mobile and desktop page speed score were 93 and 97 respectively. The PageSpeed Index and were quick enough. Manually I checked the website page and it loaded quickly enough.

From the above results we can say that, without using any WordPress plugins and good hosting like SiteGround, page loading time can be reduced to below 1s or 2s, both on mobile and desktop.

Case 2: Some Plugins Activated

Later, I activated some of the important plugins after clearing the Cloudflare cache. I used the testing tool services on Microsoft Edge browser.

1. AMP for WP – Accelerated Mobile Pages ( Ahmed Kaludi, Mohammed Kaludi)
2. Akismet Anti-Spam (Automattic)
3. Classic Editor (WordPress contributors)
4. SG Optimizer (Siteground)
5. Wordfence Security (Wordfence)

The same web page was tested to check the loading time and score results of the tool.

I got a PageSpeed Score of A(98%) and YSlow Score(94%). The fully loaded time was 1.2s, 147KB page size and 15 requests.

The same test when carried on Pingdom tools, it gave a performance grade of B(82). The load time was 1.59s and page size was 150.7KB and took 19 requests.

The AMP page tested with Google PageSpeed Insights testing tool produced a score of 84. The first meaningful paint time was 1.0s and speed index was 5.5s. The desktop score was 96.

All the lab data parameters of the tool were green, except for speed index which was showing 1.5s.

Case 3 : Other Plugins Activated

In addition to the above plugins, the following plugins were activated.
6. Contact Form 7 (Takayuki Miyoshi)
7. Cookie Notice (dFactory)
8. EWWW Image Optimizer (Exactly WWW)
9. kk Star Ratings (Kamal Khan)
10. Lightweight Subscribe To Comments (Isabel Castillo )

After activating the above plugins, cloudflare, siteground and browser cache was cleared and checked for results.

In the GTMetrix test, it was observed that fully loaded time was 3.4s, after two iterations. The total page size was 487KB and required 48 requests. The PageSpeed Score was A(90%) and YSlow Score was B(82%).

The page loading time almost tripled and page size was also bigger. So the resource hog or performance bottleneck that was causing slow page load time should be one of the above plugins.

Contact Form 7 Slows down your WordPress Website

So I decided to deactivate EWWW Image Optimizer and Contact Form 7 plugins. I already tested kk Star Ratings plugin for speed performance and it did not show any issues.

This time I did not clear cloudflare and SG Optimizer plugin cache. I cleared only browser cache in Microsoft Edge, every time I did the test.

On disabling both the plugins and clearing all the required cache, I tested the same page with GTMetrix again.

This time the page speed results were good. I got fully loaded time of 1.0s, total page size of 187KB and 21 requests. The PageSpeed Score was A(97%) and YSlow Score was A(90%). So the culprit must be one of these two plugins.

So I enabled the Contact Form 7 plugin and tested again.

This time the page loading time was 2.5s, with A(90%) and B(82%) scores respectively. The total page size was also 475KB.

So I decided to deactivate Contact Form 7 and activate EWWW Image Optimizer plugin and check the results.

Wow! I got almost the same results as in the second case. The fully loaded time was only 1.1s and total page size was also only 188KB. The scores were A(97%) and A(90%) respectively.

This indicates that outdated plugins slow down your site.

MTS Plugins Activated

11. Rank Math SEO
12. WP Review Pro
13. WP Shortcode Pro by MyThemeShop (MTS)

To clarify things better, I have been using the MTS plugins which are outdated. This is because my license expired and still using the old versions. According to MTS license conditions, you can keep the outdated plugins for further use, though new version and support is not provided.

Then I checked for the results if the MTS plugins are causing any speed throttling and performance issues.

The GTMetrix test results show PageSpeed score of B(88%) and YSlow Score of C(79%). The fully loaded time was 1.6s. But the total page size was 1.29MB. The number of requests was 56.

I just cleared the browser cache this time.

Though page speed was comparatively low, the page size and requests drastically increased. So I decided to deactivate the expired plugins from MTS. I was doubtful that since the plugins were of old version, it may cause some performance decrease.

As expected the scores improved to A(97%) and B(89%) respectively. The fully loaded time also decreased to 1.0s. Other significant improvment was that the total page size decreased to 195KB and number of requests to 23.

Conclusion

As can be see from the above test results, plugins play a major role in wordpress website page speed. If you are using old version, expired, outdated plugins they are likely to be bottlenecks in the speed performance.

It is always better to use the latest version of wordpress plugins. Another important thing is to check the support page of each plugin. If any bugs have cropped, they are generally mentioned in these forums. You can take evasive action like resorting to a version below, untill the author comes up with bug-free version.

1 comment… add one
  • alexbeglov1989 Aug 15, 2019, 7:47 pm

    Wordpress plugins play a major role in the speed of a site. This study helps to understand the role played by plugins in performance. Image optimization plugins reduce the size of images and thus improve speed. Better to look out for change in speed, after installing and activating any plugin.

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