The importance of Core Web Vitals in SEO: a complete guide in 7 points

Since May 2021, Core Web Vitals have been an integral part of Google’s ranking factors. These indicators, which measure the loading speed, interactivity and stability of web pages, have a significant impact on user experience (UX) and, therefore, on natural referencing (SEO).

Design by Freepik

The Top 3 Core Web Vitals

1. Largest Contentful Paint (LCP) 

    • Definition: the time required for the main content of a page to be visible on the screen.
    • Goal: An LCP of less than 2,5 seconds is considered good.
    • Influencing factors: image size and format, font loading time, JavaScript and CSS code, server response time.
    • Optimization tips: optimize images for the web (compression, appropriate sizing), use a CDN (Content Delivery Network), minimize JavaScript and CSS code, defer loading of non-critical scripts, optimize server response time.

2. Interaction to Next Paint (INP) 

    • Definition: The delay between when a user clicks on an element and when the page responds.
    • Goal: An INP of less than 100 milliseconds is considered good.
    • Influencing factors: JavaScript processing time, network resource loading time, user interface complexity.
    • Optimization tips: reduce JavaScript processing time, optimize network resource loading, simplify the user interface, identify and fix JavaScript performance issues.

3. Cumulative Layout Shift (CLS) 

    • Definition: the unexpected shift of the content of a page while it is loading.
    • Objective: a CLS score less than 0,1 is considered good.
    • Influencing factors: loading asynchronous content (images, videos, JavaScript), use of web fonts, advertisements, floating elements.
    • Optimization Tips : avoid loading asynchronous content on top of the main content, use web fonts with pre-loading, optimize ad size and placement, avoid floating elements.


Why are Core Web Vitals important for SEO?

Improving bounce rate and conversion 

    • Fast, responsive web pages encourage users to stay longer and take actions, like purchasing a product or signing up for a newsletter.
    • A Google study found that web pages with an LCP less than 2,5 seconds have a 32% lower bounce rate than those with an LCP greater than 4,7 seconds.
    • Another study showed that web pages with an INP less than 100 milliseconds have a 15% higher conversion rate than those with an INP greater than 500 milliseconds.

Better Google ranking 

    • Google uses Core Web Vitals as one of several signals to determine page rankings in search results.
    • Although Core Web Vitals are not the only ranking factors, they are increasingly important and can have a significant impact on your visibility in search results.

Brand perception and customer satisfaction 

    • A good user experience contributes to better brand perception and greater customer satisfaction.
    • Users are more likely to trust and return to a website that provides a fast, smooth, and enjoyable experience.


How to measure Core Web Vitals?

Google offers several tools to measure Core Web Vitals, such as:

PageSpeed ​​Insights

    • This tool allows you to analyze the performance of a web page on computer and mobile.
    • It provides a score for each Core Web Vital, along with recommendations for improvement.

Search Console 

    • Search Console provides a report on your website's Core Web Vitals.
    • This report allows you to identify pages that have performance issues and track your progress over time.

Test on different devices and browsers

The performance of a web page may vary depending on the device and browser used. It's important to test your Core Web Vitals on a variety of devices (desktops, smartphones, tablets) and popular browsers (Chrome, Firefox, Safari, etc.) to get a complete picture of your website's performance.

Third party tools

In addition to Google's tools, there are many third-party tools that can help you measure Core Web Vitals and identify performance issues. These tools can provide deeper analytics and additional features, such as continuous monitoring and historical reporting. Other tools, like GTMetrix, are not completely free.


Optimize Core Web Vitals for SEO

We have already discussed some optimization tips for each Core Web Vital. Here is additional information:

Image optimization

Use modern, compressed image formats (JPEG for photos, WebP for illustrations and graphics), resize images to their intended display size, and consider using lazy loading techniques to load images in outside the initial navigation area.

Code minification

Minifying HTML, CSS, and JavaScript code helps remove unnecessary characters like spaces and comments, reducing file size and improving loading time.

Asynchronous and lazy loading

Asynchronous loading allows scripts to load in parallel with the main content of the page, while lazy loading delays the loading of non-critical scripts until the user needs them. These techniques can improve LCP and INP by preventing scripts from blocking page rendering.

Preloading critical resources

Preloading allows the browser to proactively load critical resources like web fonts and CSS styles. This can improve initial page rendering and reduce CLS.

Browser caching

Browser caching allows you to store local copies of static files such as images and scripts. This can improve performance for returning visitors by avoiding re-downloading the same files on each visit.


Tools and Resources for Optimizing Core Web Vitals

Google provides numerous resources to help you optimize your Core Web Vitals:


Core Web Vitals in brief

Core Web Vitals are essential elements of modern SEO. By optimizing your Core Web Vitals, you will improve your website's user experience, which will positively impact your Google rankings, conversion rate and business success.

Remember that optimizing Core Web Vitals is an ongoing process. It is important to regularly monitor your performance using the tools mentioned above and make the necessary changes to maintain a quality user experience. By providing a fast, smooth and enjoyable web experience, you will retain your visitors and contribute to the long-term success of your website.



Esteban Irschfeld, SEO Consultant at UX-Republic