how web speed measurement tools work


In recent years, speed measurements have become more and more relevant when it comes to web development and implementation. If we focus on WordPress nowadays nobody considers an installation without at least a cache plugin and various optimizations.

The problem of web speed measurement tools

This trend, which is good in itself, as it goes in the right direction of offering fast websites for all types of devices and connection speeds, as well as reducing the carbon footprint, is still far from being understood by the average user in terms of the different aspects of its application.

Above all, in recent years, parallel to the lack of clear training and information aimed at all types of users, misunderstandings and myths have been accumulating, which not only do not favor the knowledge of web optimization technologies but complicate everything.

In fact, most of the tools that we usually use to measure optimization parameters and web speed are not designed for all types of users, and for that reason alone we will accumulate misunderstandings, but above all uneasiness, verifying that we do not have the technical or theoretical capabilities to apply what is indicated in these tools.

It is not that they are exclusive tools, it is simply that most of these applications are not designed for the average user, and we try to understand them and apply their indications without the necessary knowledge to do so.

The role of WordPress in web optimization for everyone

And thank goodness that in WordPress we have lots of plugins and services, almost always free, that help us to optimize our websites, otherwise, it would be practically impossible to apply all those indications of performance improvement that we usually see in the main speed measurement tools and web metrics.

Imagine having to apply all those technical enhancement concepts without the help of plugins. You would have no choice but to learn how to program or spend hundreds or thousands hiring someone to do it for you. That would be excluding.

Imagine having a website made “from scratch” in which you have to apply techniques such as defer, async, lazy load, CSS critical path and others on your own. Yes or yes you would have to hire someone, and it would not be cheap, or just for today, you would have to have someone on staff to update your website to each new optimization technology.

In fact it is especially relevant that, in the face of these new technical challenges, unaffordable for the current profile of web manager, usually the business owner, who has created his website using templates, without programming a single line of code, there is WordPress, to facilitate the application of all these optimization technologies in a simple way, and without having to ask for a loan from the bank to make your business website competitive.

Anyway, in this article I’m not going to talk about plugins, not even about WordPress, but about how to understand and correctly use those speed measurement tools that we usually use without any other criteria than knowing that they exist and that everyone uses them.

The goal is that you can take advantage of all these speed measurement tools according to your technical profile, and get the most out of each of them.

Myths about web performance tools

First of all, let’s review some of the myths that have arisen in connection with speed measurement tools.

User experience can be analyzed with a single metric

It is not possible to measure a good user experience only by analyzing a single point of measurement. From the moment the user accesses our website until he performs the action we expect, he performs a series of steps and uses of navigation that must be analyzed as a whole and separately, each one of them in its dimension and importance.

And for this there are several metrics involved, since there will be “moments” in which the most important will be the overall loading speed, while in others the most relevant will be the adaptability of the elements of the page or the simplicity of the interaction.

For example, as soon as the user arrives at our website we will want a minimum LCP, to offer a favorable impression of speed and navigation, but when it comes to obtaining the conversion through a form or product selection, the CLS will be more important, avoiding introducing elements that make it difficult for the user to click or enter data.

User experience can be assessed by “typical users”.

Reality has nothing to do with laboratory measurements performed by speed tools, each user uses a different device, in different locations, screen sizes, colors and connections, changing throughout the day or even less.

You must be able to make field study measurements taking into account variables such as connection (3G, 4G, Fiber, and at various speeds), device type (mobile, tablet, desktop), at various sizes, orientations, operating system used, active browser, etc.

There are many parameters that can confuse you when evaluating the results of measurement if you do not take into account how your users, not typical users, but your users, browse in different situations.

The reality is that you will never use a single tool to analyze the user experience in depth, but rather the confluence of several, such as PageSpeed Insights + Google Search Console + Google Analytics + heat maps and videos of real interaction.

If my website loads fast for me, it will also load fast for the rest of the users.

In line with the previous myth, the reality is that no matter how many simulators we use, the speed, networks and devices used by a developer or a web owner will never be the same as those used by different users.

I myself have several active mobiles of different operating systems and screen sizes for web development testing, but even that is not enough. Only real field analytics data, with tools that together give us a real view of the behavior and navigation of our website.

Laboratory and field data

Most optimization and speed measurement tools will provide one or both laboratory and/or field data, so it is important to know what each will be useful for.

Laboratory data

Lab data is performance data collected in a controlled environment with a predefined device and network configuration. This provides reproducible results and debugging capabilities to help identify, isolate and troubleshoot performance issues.

To collect this type of data you can use tools such as Lighthouse and WebPageTest.


  • Useful for debugging performance issues
  • Deep and comprehensive view of the user experience (UX)
  • Replicable testing and debugging environment


  • May not capture real-world bottlenecks
  • Cannot correlate to real-world page key performance indicators (KPIs)

Field data

Also called Real User Monitoring or RUM.
Field data is performance data collected from actual page loads that your users are experiencing in real life.

To get reports on this type of data you can use Chrome’s user experience report or measurement tools like PageSpeed Insights.


  • Captures the true real-world user experience
  • Enables correlation with enterprise KPIs


  • Restricted set of metrics
  • Limited debugging capabilities

Which tool should I use according to my technical profile?

At this point, and having understood what and how to measure the performance and user experience of a website, it is not the same to use one tool than another, and depending on your technical profile you should focus more on some than others, and thus make the most of these new technologies.

If you are a marketer or developer trying to optimize user experience and conversions

  • Use Speed Scorecard to analyze your site’s mobile speed compared to your peers in 10+ countries. Scores are based on actual data from the Chrome User Experience Report.
  • Use the Impact Calculator to evaluate potential revenue opportunities from improving your mobile site speed. Impact is based on Google Analytics benchmark data.
  • Use TestMySite to test your page load time on mobile devices against industry benchmarks and learn how simple fixes can speed up your site and reduce visitor churn. TestMySite is currently based on WebPageTest and PageSpeed Insights.

If you are a developer trying to know the real user experience and sectorial recommendations

PageSpeed Insights helps you understand your site’s actual performance, as experienced by Chrome users, and recommends optimization opportunities.

Developer trying to understand web performance best practices

Lighthouse contains a complete set of performance improvement opportunities. It provides you with a list of missing performance opportunities on your site and the time saved by implementing each optimization, which can help you understand what you need to do.

Developer seeking technical guidance on how to deepen web performance

The Chrome Developer Tools (CDT) contains a performance dashboard that allows you to drill down into your site’s performance issues by creating profiles with custom settings, allowing you to track performance bottlenecks. You can use CDT on both production and development versions of a website.

WebPageTest contains an advanced set of metrics and trace viewers. It allows you to drill down into your site’s performance on real mobile hardware with network conditions.

Well, that’s all for today. I hope this reflection has helped you to take better advantage of all those performance and speed tools that sometimes seem so complicated, and it is not our fault, but simply because we are not using the right one for our profile or, simply, we are not using it well for our purpose.

If you want to learn more about this whole philosophy of web performance and optimization you can check the category of articles and guides on WPO of the blog, or Google’s guides.

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