Testing your WordPress website performance with GTmetrix

Previously in this series, we’ve reviewed the Google PageSpeed Insights and Pingdom Website Speed Test services, and we’ve shared with you a few tips to keep in mind before starting to optimize your website speed. Today, we’ll take a look at GTmetrix performance analysis tool, which is another excellent service for analyzing your website performance.

Testing your WordPress website performance with GTmetrix

GTmetrix performance analysis tool is an all-in-one service to analyze your website performance, just like Google PageSpeed Insights and Pingdom Speed Test. However, GTmetrix shines by providing you with results from other services.

GTmetrix comes with free and paid plans, but you won’t need to pay unless you hit the limits of the basic (free) plan or you need specific features available only for paid plans. For now, we’ll only focus on the free features of GTmetrix, since most of the paid features are available when using GTmetrix in conjunction with other page speed test tools.

While GTmetrix is useful when you want to compare the results of different services, it doesn’t mean you should only use GTmetrix when testing the speed of your website, since it won’t necessarily give you the same recommendations given when using each tool separately.

Performance Report

GTmetrix will provide you with results from Google PageSpeed Insights and YSlow. When testing the speed of a page, GTmetrix displays the PageSpeed Score and YSlow Score, shows you a list of recommendations, and attributes a score to each of them. If the score of a specific recommendation is less than 100%, GTmetrix also tells you which files are problematic and how to fix the issue.

GTmetrix report

Waterfall Chart

Like the Pingdom Website Speed Test service, GTmetrix displays a file requests timeline, which is called Waterfall Chart. It works pretty much the same as Pingdom: for each resource loaded, you can see on the chart how long it took for the DNS Lookup, and what were the connecting, sending, waiting and receiving times. You can also take a look at the headers of each file, and even view the content of the file under the “Response” tab.

GTmetrix Waterfall Chart

Also, regarding the Waterfall chart, GTmetrix shows up to 5 vertical lines on the chart, which represent “event timing relative to the request start”, or in other words, how long it took before each of the following events happened:

  • Dom Loaded
  • First Contentful Paint (FCP)
  • First Paint
  • Onload
  • Fully Loaded

GTmetrix Waterfall Chart - Event Timing Relative to the Request Start

Report History

Another nice GTmetrix feature is the Report History. GTmetrix keeps the data generated during previous tests for a specific page, and generate charts, making it easier for you when you want to compare and see if things are going better or not. You can also download the history in CSV format.

Compare Reports

The last thing I want to share with you is the Compare Reports feature. GTmetrix compares the results for various URLs and then displays them next to each other. The overview is handy when you want to compare different pages of the same website or when you want to compare your website with other competitors.

GTmetrix Compare Reports


In the next post of this series, we’ll take a look at the DotCom-Tools Website Speed Test service, since it has something different to offer than the previous services we’ve reviewed.

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Dave Lavoie
Co-Founder of WP Captain, I'm a senior WordPress developer and solutions architect. I lead all WordPress development efforts and provide advanced customer support to our users.

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