Core Web Vitals are Google's key metrics for measuring user experience, and they play a crucial role in how your website ranks in search results.
In 2021, Google introduced Core Web Vitals as part of its ranking algorithm – a clear signal that user experience (UX) is now a critical part of SEO. But what are Core Web Vitals, and why should you care?
What are core web vitals?
Core Web Vitals are a set of three metrics that measure real-world user experience for loading speed, interactivity, and visual stability:
Largest Contentful Paint (LCP) – measures how long it takes for the largest element (e.g. image or text block) to load. Good: under 2.5 seconds
First Input Delay (FID) – measures how responsive a site is to a user’s first interaction (like clicking a button). Good: under 100 milliseconds
Cumulative Layout Shift (CLS) – measures how much the layout shifts unexpectedly while loading. Good: less than 0.1
Why do they matter for SEO?
These metrics affect how users perceive your site. If your site is slow or jumps around as it loads, users will bounce, and Google will notice.
Key reasons they impact SEO:
- Google uses Core Web Vitals in its ranking algorithm
- Better scores improve user engagement, bounce rates, and conversions
- Google’s Page Experience report includes them as a quality signal
How to measure your Core Web Vitals
You can check your score using tools such as:
- PageSpeed Insights
- Google Search Console
- Chrome DevTools
- Lighthouse
These tools offer lab and field data to help prioritise what to fix.
How to improve your Core Web Vitals
- LCP: optimise images, use faster hosting/CDNs, and remove render-blocking resources.
- FID: minimise JavaScript, use web workers, and defer unused scripts.
- CLS: always define image/video dimensions and avoid dynamic content shifts.
In summary
Core Web Vitals are more than just technical benchmarks, they reflect real user experience. Optimising them helps keep Google happy, meaning your site will rank more highly, and it will keep users happy, as the site will load faster.
Core Web Vitals FAQs.
Core web vitals are a set of performance metrics defined by Google that measure key aspects of real-world user experience — how fast content loads, how responsive the site is, and how stable the layout feels as it loads.
The three core web vitals are Largest Contentful Paint (LCP) (loading speed), Interaction to Next Paint (INP) (responsiveness, replacing First Input Delay), and Cumulative Layout Shift (CLS) (visual stability).
Google uses core web vitals as part of its page experience ranking signal, so better scores can help your site be seen as higher quality by search engines — and deliver a better user experience.
No — core web vitals are one part of SEO. Quality and relevance of content remain the strongest ranking factors, so good scores help but don’t automatically secure top positions.
You can measure them with tools like Google search console’s core web vitals report, pagespeed insights, lighthouse and chrome devtools.
Field data (real user measurements) is what google uses for ranking signals, while lab data (from tools like lighthouse) simulates performance to help diagnose issues.
Scores can vary due to real-world factors like network conditions, device differences, and server performance — so small fluctuations are normal.
Yes — Google evaluates core web vitals for both mobile and desktop performance, and it’s important to optimise for both where possible.
Regular monitoring is recommended so you can spot changes after updates or content changes and prioritise improvements where needed.
Yes — better performance and stability often lead to improved user engagement, lower bounce rates, and can support higher conversions beyond just SEO.
