Core Web Vitals are coming. What elements on the page can negatively affect performance?

photo of Marc Sendra Martorell | Unsplash

Google – despite content being most important to them – continues to raise the bar for publishers when it comes to UX as well. To determine the position of the page, it takes into account a number of indicators related to both the speed and the usability of the website. They concern, among other things, security, loading times, adaptation to mobile devices, no intrusive full-screen ads, but – as is usually the case with Google – it is not clear how much each of them weighs. ‘them. With the advent of Core Web Vitals, things are going to get even more complicated.

What is Core Web Vitals?

The Core Web Vitals initiative aims to simplify performance evaluation and identify the most important elements for evaluation. Among them, 3 universal indicators have been distinguished, the so-called Core Web Vitals, on the basis of which the UX of the website will be evaluated. Each of them represents a distinct aspect: loading, interactivity and visual stability, as well as ranges of values ​​- good, needing optimization and poor quality.

So it’s not just about how fast the entire page content loads, but all the UX aspects it affects. And everything would be simple if it weren’t for the fact that the issue of performance cannot be dealt with with a specific tool. Page load time is a result of all best practices and architectural assumptions adopted by the creators of the website, as well as – installed third-party services, including analytics.

So how to deal with it?


Mateusz Szajkowski
SEO Specialist

For a long time, Google’s algorithms operated on the principle of “mobile first” – crawlers focused more on the mobile version of the website than on the desktop version. Therefore, it is very important that our website is the best possible when it comes to the mobile version.

Core Web Vitals – new metrics to consider

In the case of a technical optimization of the website, the Core Web Vitals must be taken into account. These are basic web metrics that can help you gauge how satisfied users are with their interaction with our site. It is said that in the near future, Core Web Vitals will be much more important than before, so it is worth preparing pages for core indicators.



According to Core Web Vitals, you should focus on:

  • LCP (Largest Contentful Paint) – The time that elapses between the start of the page load and the display of the largest element (currently – a block of text or an image – also inserted in the background in the worksheet style).
  • FID (First Input Delay) – the time that elapses between the user’s first interaction with the website (for example, clicking a button) until the browser reacts to this action.
  • CLS (Cumulative Layout Shift) – A cumulative measure of unexpected page element shifts.

Taking care of these 3 fundamental indicators, according to Google should result in good website performance.

What elements of the website can negatively affect the indicators mentioned above?

  1. A large number of elements loaded with scripts, Java Script and CSS code – it can be any transition button, on-page animations, page beautification elements (strongly related to UX)
  2. Images not optimized on the page (high photo resolution, wrong aspect ratio)
  3. Using GIFs and videos in the background

How to approach these elements?

If we use scripts, remember to use them wisely – the less Java Script code the better for our website performance. If we use scripts, remember that the files containing the script should weigh as little as possible and be as small as possible. It is worth looking into minifying JS and CSS code and combining many files into one.

You should always optimize the images on the website. It is important that the resolution of the photo is always adjusted to the field in which the image will be displayed. A very effective solution is the use of ‘Lazy Load’, a method whose use prevents the browser from downloading resources that are off screen. In addition, you can always think of a gentle compression of photos, in many cases the drop in quality is practically invisible, and thanks to the compression the images weigh much less.

We don’t use gifs and videos if it’s not necessary. Such elements significantly deteriorate the performance of the website and, in many cases, we are not able to optimize them.

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