6 Metrics to Evaluate Your Website’s Performance

Managing a website involves more than keeping it up to date. You need to closely monitor its performance to see whether it is meeting its goals. 

To do this, there are specific metrics you should analyze and study in detail. Check out 6 metrics you can use to evaluate your website’s performance. 

1 - Largest Contentful Paint (LCP)

Measuring how quickly content loads on a web page and how long it takes to become visible to users is extremely important, but also a challenge for developers. 

The most complex metric is not always the best one. One of the most accurate ways to measure how quickly content loads on a page is to check when its largest element was rendered.

The Largest Contentful Paint metric shows how long it takes to render this largest element in the viewport. 

2 - First Contentful Paint

This metric is not just about a website’s response time. It focuses on the user experience and what users notice first on the site, not what loads in the background. 

By optimizing the first content displayed on your website, you not only speed up loading time, but also improve the page’s speed score and show visitors that their requests are being handled and that loading has not stalled. 

Your website’s First Contentful Paint is the moment when the browser renders the first DOM element on your page. This includes images, non-white canvas elements, or blocks of text. 

Put simply, it is when users can see some part of the page change, often as a header bar or background image. This element may not be the first thing rendered, but it will be the first thing users can see, making it essential to your website’s UX. 

3 - Time to Interactive

This performance metric measures your website’s responsiveness and loading. It helps identify when a page appears interactive but actually is not. A fast TTI helps ensure the page is usable. 

This metric is important because it is user-centered and measures how quickly visitors can fully interact with your page. For website visitors, a slow TTI can make the site seem unresponsive, broken, or not working. 

4 - Speed Index

This metric measures how quickly content is displayed while a page loads. It depends on the size of the browser viewport and is not a milestone on your page’s loading timeline, which sets it apart from other metrics such as First Contentful Paint (FCP) or Largest Contentful Paint (LCP).  

It is the result of a calculation that reflects your visitor’s experience of the page, using a frame-by-frame analysis of its loading behavior. 

Speed Index is closely related to other page loading times, making it a useful overall reference for evaluating your website’s performance as a whole. 

5 - Total Blocking Time

Total Blocking Time is one of Lighthouse’s performance metrics and was introduced in 2020. It quantifies how responsive your page is to user input as it loads. In other words, it measures the total time your web page is blocked, preventing users from interacting with it. 

The browser uses what is called the main thread to parse HTML, build the DOM, execute CSS and JavaScript, process user events, and perform other important tasks.

When any of these tasks takes more than 50 ms, the main thread is considered “blocked” because the browser cannot interrupt a task that is already in progress.

If the main thread is blocked, your page cannot respond to user input, such as screen taps, key presses, or mouse clicks. The time beyond 50 ms is considered the individual blocking time for that task.

The sum of all these blocking times is your page’s Total Blocking Time. 

6 - Cumulative Layout Shift

Also introduced by Lighthouse in 2020, Cumulative Layout Shift measures unexpected movement of web elements while a page is being rendered. It is quantified as an aggregate score of all the individual layout shifts on your page. It is one of the metrics that make up Google’s Web Vitals.

A website with a low CLS has a stable page display, with elements that do not shift, ensuring that all site content loads consistently and predictably. 

Otherwise, as a page loads, certain elements shift unexpectedly, affecting user interaction. These elements may include buttons, images, videos, contact forms, or others. 

Google PageSpeed Insights

In addition to the 6 metrics listed above, Google PageSpeed Insights is also very helpful for analysis and identifying the optimizations needed. It rates website speed on a scale from 1 to 100. The higher the score, and from 80 points onward, the better. According to Google’s criteria, a score in this range is considered good.   

It is therefore clear how important it is to analyze your website and monitor these metrics regularly to ensure the best experience for your visitors.