Introduction
Ever clicked on a webpage only to wait endlessly for it to load? It's frustrating, right? Page speed plays an indispensable role when it comes to user experience on websites.
To name just a few, performance metrics of that get negatively influenced when a page is slow:
- Bounce rate: Users hate to wait on websites. Attention spans are shorter. If a website needs too long to load, the users will bounce.
- SEO ranking: Google also ranks websites based on page speed through the Core Web Vitals. So fast, websites get higher rankings.
- Conversion rates: If a website provides a good user experience without many waiting times, it's more likely that they click through the entire customer journey and convert in the end.
So there are good reasons to optimize page speed. When trying to speed up a website, it can be hard to keep track of how fast the pages are actually loading. If it's not done properly, important things that could help increase page speed might be overseen or forgotten. Therefore, in this article, the fundamentals of page speed monitoring are discussed.
But first it's important to differentiate between two words that are often used as synonyms, even if they are definitely not. These words are measuring and monitoring. Measuring means taking a snapshot of the performance metrics at a certain point of time. But this is only one value. There is no comparison if the value is good or bad. Monitoring, on the other hand, describes the observation of performance metrics over time. It also includes the highlighting of anomalies and the assessment of trends. Monitoring is the activity we want to focus on in this article.
The most important KPIs for page speed monitoring
This article covers six so-called web vitals defined by Google, which are also relevant for SEO. The first three metrics in the table below are called “Core Web Vitals” and are the most important ones.
Different tools for monitoring page speed
There are three different categories of monitoring tools. The first categories are tools that evaluate pages based on lab results. That means, the data consists of performance information gathered within a controlled setting, utilizing predetermined device and network configurations to assure comparability. Lighthouse and Speed Kit's Page Speed Analyzer fall into this category.
It's important to mention that those applications only show the before mentioned snapshots. An external space would be necessary to monitor the data over time. Because of the controlled environment and the possibility to generate reproducible results, Lab data is really helpful for debugging performance issues. Additionally, there are many free tools to conduct lab tests, while most of the tools that work with real life data have to be purchased. On the other hand, lab results might not reflect real life user experience, bottlenecks and KPIs since the used setup is predetermined and standardized.
The second category contains tools that use real user data but not cover all the data available. The Google CrUX report is an example of this category. Through the looker studio application, it's possible to examine page speed data over time. Page Speed Insights uses lab data as well as real user data. But tools in the second category only take parts of the real user data into account. For example, the CrUX report only includes data from chrome users who accepted the cookies and are logged into their Google accounts.
The third category contains Real User Monitoring (RUM) tools. Those consider all user data and allow monitoring page speed over time. Click here to learn more about the difference between CrUX and RUM data. Some tools also implement the CrUX report in the RUM dashboard, so CrUX and RUM data can be compared. This is extremely useful, for example, for fixing Layout Shifts. Tools like Debugbear allow this, but also Speed Kit will provide this for its customers in the future.
RUM Tools have the advantage that the real-world user experience is captured with all its factors. Through this, it's also possible to create connections to business KPIs. On the other hand, sometimes the amount of data is not high enough to calculate all the necessary metrics. Also, real-world influences make reproducible results and debugging difficult. The best is to use all categories of tools and compare the results to fully grasp the performance of the website.
Running page test experiments
Finally, it also has to be clear if the changes made to optimize the website were successful. The best way to do this is to conduct a page speed experiment. The definition of an experiment is that there are two groups. One gets a treatment. The other is a control group. All other variables are kept constant. That way, it's certain that if there was a performance change resulting from the treatment, and it's possible to statistically evaluate the experiment with A/B test statistics.
One advantage of Speed Kit is that its impact can be tested through experiments. It's possible to create different user groups, so there can be a treatment and control group while both groups experience every other event on the website, meaning holding all other potential variables constant. Therefore, its always sure that Speed Kit has the promised effect.
Conclusion
This article has shown the differences between measuring and monitoring, what the most important page speed KPIs are, what different categories of tools exist and what the best way is to determine if the changes on a website had a positive effect on page speed. With these insights, fundamental knowledge about page speed monitoring is provided that can be extended through the links in this article.
