Core Web Vitals – what it is and how to improve page performance

Core Web Vitals is a set of three key metrics – LCP, FID and CLS – which Google has recognised as an important ranking factor since May 2021. They not only affect SEO, but also improve user experience by reducing bounce rate and increasing engagement. Find out why optimising these metrics is crucial for a website’s success and how to improve them effectively using proven techniques and tools.

Core Web Vitals – what are they and why are they important?

Core Web Vitals is a set of three key metrics that assess the quality of user experience on websites. They consist of three main elements:

• page load speed (LCP – Largest Contentful Paint),
• interactivity (FID – First Input Delay),
• visual stability (CLS – Cumulative Layout Shift).

Their aim is to check how efficiently a page responds to visitors’ actions and whether it provides comfortable browsing conditions.

Since May 2021, Core Web Vitals have become an important ranking factor in Google’s algorithms. Good results in these metrics not only improve a site’s position in search results, but also increase organic traffic. What’s more, optimising these parameters improves user experience by reducing bounce rate and strengthening engagement.

The importance of Core Web Vitals goes beyond SEO aspects – it is also a matter of visitor satisfaction. Fast content loading, immediate response to interactions and the absence of unexpected element shifts while browsing are factors that directly translate into user satisfaction. In the age of digital competition, looking after these metrics becomes crucial for maintaining a competitive edge and building lasting relationships with your audience.

1. 01Key metricsQuality of user experience.
2. 02Browsing comfortFast response from the site.
3. 03Google SEO rankingHigher position, more traffic.

Optimisation for better results and user satisfaction.

Basic web metrics

Core Web Vitals are three key metrics that assess a website’s performance from the user’s perspective. They consist of:

• LCP (Largest Contentful Paint) – measures the time needed to display the largest visible element, e.g. a heading or image. To ensure an optimal experience, it is worth aiming for a score below 2.5 seconds,
• FID (First Input Delay) – determines the delay between the first click and the page’s response. The ideal value is less than 100 milliseconds, which guarantees smooth interaction,
• CLS (Cumulative Layout Shift) – assesses the stability of the page layout by checking whether elements move during loading. A value below 0.1 is considered desirable.

These parameters are of huge importance not only for search engine optimisation (SEO), but also for user satisfaction. Better results translate into a lower bounce rate and greater visitor engagement. To monitor these metrics and identify areas that need improvement, it is worth using tools such as Google PageSpeed Insights or Google Search Console. Thanks to them, you can effectively tailor the site both to the requirements of search engine algorithms and to user expectations.

Impact on user experience

Core Web Vitals play a key role in shaping user experience, which directly affects how satisfied visitors are with the site they visit. Page load speed (LCP), interaction smoothness (FID) and visual stability (CLS) are the three main factors that determine whether browsing will be pleasant and trouble-free. Good results in these areas mean that users are more willing to engage with content and are less likely to stop using the site.

To ensure an optimal experience, it is worth aiming for LCP below 2.5 seconds – this ensures that the most important page elements appear quickly, minimising frustration. FID kept below 100 milliseconds guarantees an immediate response to clicks or other actions, which is particularly important for forms or buttons. In turn, CLS below 0.1 eliminates unexpected shifts of elements during loading, preventing accidental interactions and improving readability.

Good user experiences not only reduce the bounce rate, but also increase engagement. Pages that meet the requirements of Core Web Vitals are more often recommended by visitors and are better assessed by Google algorithms. That is why optimising these metrics becomes not only crucial for SEO, but also for building a positive brand image online.

1. 01Official ranking factorElement of Google algorithms
2. 02Measures user experienceOptimal LCP, FID, CLS
3. 03Better visibility and trafficHigher positions in SERPs

Key takeaways: Core Web Vitals have become an important element of how Google evaluates websites, directly affecting their position in search results and organic traffic.

The role in SEO and positioning

Core Web Vitals play a key role in SEO and website positioning. Since May 2021, they have become an official ranking factor in Google algorithms, which means that their optimisation has a direct impact on a website’s position in search results. Good results in LCP, FID and CLS not only improve visibility in SERPs, but also attract more organic traffic.

Page load speed (LCP) is one of the most important elements affecting rankings. Pages that load in less than 2.5 seconds are favoured by Google algorithms, which increases their chances of achieving higher positions. Equally important is interactivity (FID) – delays below 100 milliseconds ensure smooth site performance, which is appreciated by both users and crawling bots.

Another key factor is visual stability (CLS). Values below 0.1 guarantee that page elements do not move during loading. This minimises user frustration and has a positive effect on how algorithms evaluate the site.

Optimising Core Web Vitals brings benefits not only for SEO. It improves user engagement and reduces the bounce rate. Pages that meet these requirements are more often recommended and are better assessed by visitors, which translates into long-term benefits for the brand.

What do Core Web Vitals metrics cover?

Core Web Vitals focus on three key areas that shape the user experience on a website: loading speed, responsiveness and visual stability. Each of these factors plays an important role in how visitors perceive and use the website.

• LCP (Largest Contentful Paint) – measures the time needed to load the largest visible element on the page, such as a heading, image or main content section. The optimal LCP value should be below 2.5 seconds. Longer loading times can irritate users and lead to more people leaving the page.
• FID (First Input Delay) – assesses the delay between the user’s first click and the page’s response. Ideally, the FID value should be lower than 100 milliseconds. High delays make the page seem unresponsive, which negatively affects user experience.
• CLS (Cumulative Layout Shift) – analyses the visual stability of the site by checking whether elements move during page loading. The recommended CLS value is less than 0.1. Unexpected shifts can lead to accidental clicks or make content harder to read, which frustrates visitors.

These three metrics are not only important for SEO and visibility in search results, but also directly affect user satisfaction. Good Core Web Vitals results translate into a smoother and more enjoyable browsing experience, which in turn increases visitor engagement and loyalty.

1. 01PageSpeed InsightsDetailed reports and suggestions
2. 02Search Console (CrUX)Real user data
3. 03Chrome DevToolsA tool for developers

Discover tools for precise analysis and optimisation of performance metrics (LCP, FID, CLS).

Three key metrics: LCP, FID, CLS

LCP (Largest Contentful Paint) is a metric measuring the time needed to display the largest visible element on a page, such as a heading, image or main content section. To ensure a comfortable user experience, it is worth aiming for a value below 2.5 seconds. Longer loading times can put visitors off and lead to an increase in the bounce rate.

FID (First Input Delay) measures the delay between a user’s first interaction and the page’s response. The optimal value is less than 100 milliseconds – the lower, the better. High delays make the page feel unresponsive, which negatively affects the user experience.

CLS (Cumulative Layout Shift) assesses the visual stability of a page by detecting unexpected shifts in elements during loading. The recommended value is below 0.1. Such changes can lead to accidental clicks or make the content harder to read, frustrating visitors and lowering their satisfaction.

These three metrics – LCP, FID and CLS – are crucial both for SEO and the quality of the user experience. Good results in these areas translate into smoother browsing and greater visitor engagement and loyalty.

Interactivity and visual stability

Interactivity and visual stability are the foundations that shape the user experience on a website. Interactivity, measured using FID (First Input Delay), determines how quickly a website responds to a visitor’s first actions, such as clicking or typing text. To ensure smooth and immediate responses, the optimal FID value should be below 100 milliseconds. Longer delays can make the page seem sluggish, discouraging users from continuing to use it.

By contrast, visual stability, assessed by CLS (Cumulative Layout Shift), checks whether page elements move unexpectedly during loading. The ideal CLS value is less than 0.1. Sudden shifts can lead to frustration, causing accidental clicks or making the content harder to read. This is particularly important for pages with a lot of dynamic components, such as ads or multimedia.

Both of these aspects – interactivity and visual stability – are crucial both for user convenience and for how Google’s algorithms assess the page. Good results in these areas translate into a lower bounce rate and greater visitor engagement. Fast response times and a consistent layout are the key to the success of any website.

How do Core Web Vitals affect page performance?

Core Web Vitals play a key role in website SEO. Since May 2021, they have become an official part of Google’s algorithms, affecting website visibility in search results. Metrics such as LCP (Largest Contentful Paint), FID (First Input Delay) and CLS (Cumulative Layout Shift) are not only a measure of page performance, but also determine its position in the SERPs. Pages achieving optimal results in these metrics have a better chance of ranking higher, which directly translates into growth in organic traffic.

LCP is responsible for the loading speed of the most important elements on a page. Google’s algorithms prefer values below 2.5 seconds, which has a significant impact on a website’s visibility. By contrast, FID measures responsiveness – delays shorter than 100 milliseconds ensure smooth interactions, appreciated by both users and indexing robots. Meanwhile, CLS assesses visual stability – values below 0.1 eliminate unexpected shifts in elements during loading, which minimises visitor frustration.

Taking care of Core Web Vitals is not just a matter of better SEO. Pages with optimal results are characterised by a lower bounce rate and higher user engagement. This in turn translates into a better assessment of the website by algorithms and the building of visitor loyalty.

It is worth emphasising, however, that Core Web Vitals are only one of many factors affecting ranking. High-quality content and other technical aspects also matter enormously for SEO. Nevertheless, optimising these metrics can prove crucial, especially when pages compete with each other in terms of content quality and technical parameters.

SEO in search results

Page visibility in search results is inseparably linked to the optimisation of Core Web Vitals. These key metrics – LCP (Largest Contentful Paint), FID (First Input Delay) and CLS (Cumulative Layout Shift) – have a direct impact on SEO. Since May 2021, Google has officially taken them into account in its ranking algorithms, which means that websites achieving better results in these areas have a greater chance of higher positions in SERPs.

LCP is responsible for how quickly the most important elements of a page load. To meet Google’s requirements, it is worth aiming for a value below 2.5 seconds – this not only improves visibility, but also has a positive impact on user experience. FID, in turn, measures the responsiveness of the website; delays shorter than 100 milliseconds guarantee smooth interactions, which are appreciated by both visitors and indexing algorithms. Meanwhile, CLS assesses the stability of the page layout – values below 0.1 eliminate unexpected shifts in elements during loading, which significantly reduces user frustration.

Caring about Core Web Vitals brings benefits that go beyond SEO alone. Pages that meet these standards are recommended more often by visitors, which translates into a lower bounce rate and greater engagement. This, in turn, builds long-term brand value and strengthens its online presence.

User comfort and bounce rate

User comfort and bounce rate are inseparably linked to Core Web Vitals performance. Metrics such as LCP, FID and CLS play a key role in shaping user experience, which directly translates into a lower bounce rate. Pages that load in the blink of an eye (LCP below 2.5 seconds), respond instantly to user actions (FID below 100 milliseconds) and maintain visual stability (CLS below 0.1) attract more visitors and encourage longer browsing.

Slow page loading or unexpected shifts in elements often lead to frustration, which results in a high bounce rate. Optimising Core Web Vitals helps eliminate these problems, increasing user satisfaction. According to research, websites that meet these standards can achieve a 24% lower bounce rate compared with those with poorer performance.

What is more, better user experiences translate into greater engagement and loyalty. Internet users are more likely to return to pages that are fast and intuitive to use. This, in turn, affects the brand’s long-term success and its position in search results.

How to improve Core Web Vitals? Practical tips

To improve Core Web Vitals performance, it is worth implementing several practical solutions that will significantly increase page performance. Start with optimising loading time (LCP). One effective method is image compression to the WEBP format, which provides smaller file sizes without loss of quality. In addition, using the Lazy Load technique allows you to delay loading images and other resources until they are actually needed by the user.

Another key element is improving interactivity (FID). To achieve this, minimise the use of scripts that block page rendering and introduce asynchronous scripts. This allows the browser to process different elements of the site in parallel, which shortens the response time to the user’s first actions.

Do not forget about visual stability (CLS). To avoid unexpected shifts in elements during page loading, assign predefined dimensions to images and other dynamic content. Using placeholders for photos or videos prevents sudden layout changes, which significantly improves user experience.

It is also worth optimising HTML, CSS and JavaScript code through minification and removing unnecessary fragments. Regular monitoring of results using tools such as Google PageSpeed Insights or Google Search Console allows you to identify areas requiring improvement on an ongoing basis and adapt the optimisation strategy to the website’s current needs.

Server configuration also has a huge impact on performance. Implementing the HTTP/2 protocol and enabling resource caching can significantly speed up page loading time. Also consider using Content Delivery Network (CDN), which distributes content from servers located closer to the user.

These actions not only improve Core Web Vitals results, but also translate into greater user comfort and better positioning in search results.

Optimising loading time and interactivity

Optimising the loading time and interactivity of a website is a key element affecting its performance. To achieve better results, it is worth using several proven techniques.

• start with image compression to the WEBP format, which offers smaller file sizes without loss of quality; as a result, the largest elements of the page (LCP) can load up to 30% faster,
• use Lazy Load, i.e. delayed loading of images and other resources until they appear in the visible area of the browser, which significantly reduces the load during the first visit to the page,
• minimise browser blocking by JavaScript scripts; introducing asynchronous scripts allows different elements of the site to be processed simultaneously, which translates into better responsiveness (FID),
• clean HTML, CSS and JavaScript code of unnecessary fragments and apply file minification,
• assign predefined dimensions to images and other dynamic content to improve visual stability (CLS); using placeholders prevents sudden shifts in elements during page loading, which eliminates user frustration and improves their experience.

Implementing the HTTP/2 protocol and enabling resource caching on the server are further ways to speed up website performance. Also consider using a Content Delivery Network (CDN), which distributes content from servers located closer to the user, which further shortens loading time.

These actions not only contribute to better Core Web Vitals results, but also improve user comfort and the website’s SEO in search results.

Layout stability and visual consistency

The stability of a website’s layout and its visual consistency play a key role in shaping user experience and results related to Core Web Vitals. To achieve optimal performance, it is worth using a few proven methods.

The first step is to set fixed dimensions for graphic elements such as images or videos. This allows the browser to reserve the appropriate space before the content loads, preventing unexpected shifts during page loading. This directly improves the CLS (Cumulative Layout Shift) metric, which should stay below 0.1.

Another important aspect is using placeholders for dynamic content, such as ads or multimedia. They act as temporary containers that keep the page layout stable even when resources are not yet fully available. This minimises the risk of sudden visual changes that can irritate users and worsen their experience.

Optimising CSS and JavaScript code is no less important in order to avoid blocking the rendering process. It is worth loading scripts asynchronously or delaying their execution until they are actually needed. This approach has a positive impact on the page’s interactivity (FID) and its visual stability.

Implementing these practices not only improves Core Web Vitals results, but also increases user satisfaction and the website’s SEO in search results. As a result, the site becomes more user-friendly and is rated more favourably by Google’s algorithms.

Using asynchronous scripts and Lazy Load

Asynchronous scripts and the Lazy Load technique are proven ways to improve website performance, with a direct impact on the key indicators of Core Web Vitals. These metrics assess user experience, and optimising them can significantly affect how a website is perceived. Asynchronous scripts make it possible to load resources such as JavaScript at the same time without interfering with the rendering process. As a result, the browser displays content faster, which translates into better LCP (Largest Contentful Paint) and FID (First Input Delay) results.

In turn, the Lazy Load technique delays loading images, videos or other multimedia elements until the user scrolls the page to their location. This solution reduces the load during the initial page visit, speeding up its performance and improving interactivity. As a result, visitors experience less delay in the page’s responses to their actions.

To implement these methods effectively:

1. add the async or defer attribute to JavaScript scripts to avoid blocking rendering,
2. apply Lazy Load to images and other multimedia resources,
3. set predefined dimensions for graphic elements, which will prevent unexpected shifts (CLS).

These practices not only improve Core Web Vitals results, but also increase user satisfaction and the website’s SEO in search results. Thanks to them, the site becomes more responsive and user-friendly.

Image compression in WEBP format

Image compression in WEBP format is one of the most effective methods of speeding up website loading. Thanks to this format, it is possible to significantly improve Core Web Vitals metrics, especially LCP (Largest Contentful Paint), which is crucial for user experience. Compared with traditional formats such as JPEG or PNG, WEBP offers file sizes up to 30% smaller while maintaining excellent image quality. This means that the most important elements of the site load faster, which translates into greater visitor satisfaction.

For online stores, where the number of product images is usually huge, implementing WEBP compression becomes particularly important. On platforms such as PrestaShop, you can easily install dedicated modules that automatically convert images to this format. This not only speeds up the site, but also reduces data usage for mobile users – which is extremely important in times of smartphone and tablet dominance.

WEBP also stands out for its versatility – it supports transparency and animations, making it an ideal solution for a variety of graphic content. What is more, most modern browsers, such as Chrome and Firefox, natively support this format. As a result, there is no need for additional technical solutions or conversion to other formats.

Optimising images with WEBP is not just a matter of performance. Better LCP results can affect higher positions in Google search results and reduce the bounce rate. Studies show that sites with optimal Core Web Vitals parameters can record a bounce rate even 24% lower than those without optimisation.

Implementing this technology is straightforward thanks to available tools and integrations with popular CMS platforms. Regular monitoring of results using tools such as Google PageSpeed Insights allows you to adjust your strategy on an ongoing basis and maintain high site performance.

Tools for measuring Core Web Vitals

A wide range of tools is available for analysing Core Web Vitals, helping you to examine website performance in detail. One of the most popular is Google PageSpeed Insights. This solution provides detailed reports on key metrics such as LCP, FID and CLS. What is more, it not only assesses the results, but also suggests specific steps for optimisation.

Another tool worth noting is Google Search Console, especially the CrUX (Chrome User Experience Report). It collects data from real Chrome users, which makes it possible to obtain reliable information about visitors’ experiences. This makes it easy to detect issues occurring on different devices or in different regions.

Developers also often use Chrome DevTools. This advanced tool enables real-time analysis of website performance. It lets you track individual metrics while the site is loading and identify elements that may be slowing it down.

If you are looking for a simpler solution, it is worth trying the Web Vitals Extension for Chrome. This plugin enables you to monitor Core Web Vitals directly in the browser. It is particularly useful when testing changes on a website.

You should also not forget about Lighthouse, available both as a Chrome extension and as part of Chrome DevTools. Lighthouse generates comprehensive reports on performance, accessibility and SEO, making it a versatile tool for optimising websites.

All of these solutions not only help measure Core Web Vitals, but also provide practical tips for improving results. Using them regularly helps maintain high site performance and deliver a better experience for users.

Google Pagespeed Insights

Google PageSpeed Insights is an extremely useful tool that allows you to examine website performance in detail. It analyses key metrics such as LCP (Largest Contentful Paint), FID (First Input Delay) and CLS (Cumulative Layout Shift), which have a huge impact both on user experience and on a site’s position in search results.

However, it does not stop at evaluation alone – it also provides practical optimisation guidance. If, for example, a site has problems with the loading speed of main elements (LCP), the tool may suggest converting images to the WEBP format or using Lazy Load. When there are delays in interactivity (FID), it often recommends reducing render-blocking scripts.

It is worth emphasising that Google PageSpeed Insights tests performance on both mobile devices and desktop computers. This is particularly important because more and more people browse websites using smartphones. The tool also draws attention to visual stability (CLS), helping to avoid irritating shifts in elements while the page is loading.

Using this solution regularly makes it possible to track Core Web Vitals results and implement the necessary fixes on an ongoing basis. As a result, not only does the site’s position in Google rankings improve, but user satisfaction also increases. This, in turn, can lead to a lower bounce rate and greater visitor engagement.

Google Search Console and the CrUX report

Google Search Console provides the CrUX (Chrome User Experience Report), which collects data from real Chrome users. This tool provides reliable information about visitors’ experiences, enabling a precise analysis of key Core Web Vitals metrics such as LCP, FID and CLS. This report is particularly useful for monitoring site performance across different devices and in different geographic regions.

The data from the CrUX report is used by Google to assess website quality, which directly affects its position in search results. The tool helps identify issues related to:

• loading speed,
• interactivity,
• visual stability.

These factors can have a significant impact on user satisfaction.

In Google Search Console you will also find detailed guidance on site optimisation. Based on the data from the CrUX report, you can take specific actions such as:

• improving the loading time of the largest elements (LCP),
• reducing delays in interactivity (FID),
• eliminating unexpected shifts in elements while the page is loading (CLS).

Using the CrUX report regularly allows you to monitor Core Web Vitals results and implement the necessary fixes on an ongoing basis. As a result, the site can achieve better outcomes both in terms of SEO and user comfort. This translates into a lower bounce rate and greater visitor engagement.

Screaming Frog and using the Google Search Console API for CWV

Screaming Frog is a highly regarded website analysis tool that works excellently with the Google Search Console API. Thanks to this integration, you can efficiently monitor and optimise key Core Web Vitals (CWV) metrics. The application provides detailed information on site performance, highlighting specific areas requiring improvement. It automatically collects important metrics such as:

• LCP (Largest Contentful Paint),
• FID (First Input Delay),
• CLS (Cumulative Layout Shift).

For owners of large websites, integration with Google Search Console is a real time-saver. Manually checking every subpage would be extremely time-consuming, and Screaming Frog generates precise reports that help to understand which elements affect the deterioration of CWV performance. As a result, you can quickly spot issues such as oversized images or JavaScript scripts slowing down interactivity.

To use this functionality, you only need to configure a connection to the Google Search Console API using OAuth 2.0 authorisation. Once connected, the tool allows data to be exported to CSV or Excel formats, which makes further analysis and planning of optimisation activities easier. This means you can react quickly to page performance issues, which translates into better user experiences and higher positions in search results.

Screaming Frog also offers additional features supporting CWV optimisation. The tool allows you to analyse the site structure and identify technical errors, making it a comprehensive solution for SEO specialists and people working on website performance. This versatile tool is an invaluable aid in the pursuit of technical excellence for your website.