Web Performance refers to how a website loads. Historically, web performance was closely linked to the loading speed of a website. Nowadays, it is also linked to the quality of the user experience.
Is It fast? Can the user interact in a smooth way? Is the layout of the page displayed in a stable way?
This article gives an introduction to what Web performance is, how to measure it, and how to know if a website is performing well.
How do you measure web performance?
Two ways exist to measure Web Performance: With Synthetic and Real User Monitoring tools.
Real User Monitoring tools:
They capture Web performance metrics while users are visiting web pages in a real context. The goal is to understand the distribution of a website audience better. We can better identify pain points and prioritize optimizations thanks to users’ data.
>Read our article on how to validate your site speed optimization efforts
Synthetic performance tools:
They do an emulation of a Web page loading and measure some metrics.
Synthetic tools are useful for debugging site speed and performance issues. Since they audit Web performance in a controlled context, they can’t represent the real user experience.
Developers use synthetic tools for auditing and finding optimization hints. Unfortunately, these tools introduced a kind of score obsession. In effect, developers and managers focus too much on synthetic scores and forget that they don’t represent users.
>Read our guide on how to avoid Website speed test pitfalls
How do you know if a website is performing well?
Measure and monitor its speed/performance!
If you care about your users, you should capture real user data thanks to a Real User Monitoring tool. Google created and made public the CrUX dataset. This helps site owners to explore their website users’ data, monitor it over time, and compare it to other websites. Despite CrUX only reporting Chrome data, it is a valuable dataset for web performance.
I created a free tool, a tool that allows you to easily explore and Visualize CrUX data without writing a line of code! Check your Web Vitals now
User experience quality thresholds:
Google introduced the Web Vitals initiative to simplify the assessment of the Web performance of websites. To pass the Web Vitals evaluation, real users’ data must reach at least 75% of the good threshold on each of the metrics (LCP, FID, and CLS).
Largest Contentful Panint (LCP) thresholds:
Cumulative Layout Shift (CLS) thresholds:
First Input Delay (FID) thresholds:
