In short
The Core Web Vitals are a set of measurable metrics defined by Google that describe the actual quality of a website as experienced by the user. Instead of speaking about "speed" in general, Google breaks the user experience down into three concrete, measurable dimensions: how quickly does the main content become visible?
How quickly does the page react to input? And how stable does the layout remain while the page is loading? The Core Web Vitals are part of the overarching "page experience" signals and have fed into Google rankings since 2021.
The three core metrics
As of 2024/2025, the Core Web Vitals consist of three metrics:
- Largest Contentful Paint (LCP) measures perceived loading: when has the largest visible element in the viewport (usually an image or a large block of text) finished loading? Target value: under 2.5 seconds counts as good, over 4.0 seconds as poor.
- Interaction to Next Paint (INP) measures responsiveness: how long does it take from a user interaction (click, tap) to the page's visible reaction? In March 2024, INP replaced the earlier metric First Input Delay (FID), because it reflects the entire interaction behaviour over the page visit, not just the first input. Target value: under 200 milliseconds counts as good.
- Cumulative Layout Shift (CLS) measures visual stability: how much does the layout jump during loading, for example because an image is loaded without reserved space or a banner slides in? Target value: under 0.1 counts as good, over 0.25 as poor.
Lab data versus field data
One central point that is often overlooked: for rankings, Google evaluates the Core Web Vitals on the basis of field data, i.e. real measurements from real users, collected in the Chrome User Experience Report (CrUX). Tools such as Lighthouse or PageSpeed Insights, on the other hand, often deliver lab data from a simulated environment. The two can differ. For the SEO assessment, what counts is what Search Console reports from the field data, not a one-off Lighthouse score on the developer's laptop.
Why the Core Web Vitals matter for e-commerce
For online retailers, the Core Web Vitals are doubly relevant for two reasons. First, as a ranking factor: they are not the strongest lever (relevance and content carry more weight), but with comparable relevance they can tip the balance. Second, and often more importantly, as a conversion factor: a slow, unstable page frustrates visitors and costs sales, regardless of ranking. Studies by Google and large retailers show again and again that even small improvements in loading time have measurable effects on the bounce rate and on completed orders.
Shops in particular are susceptible: large product images drive up LCP, a lot of JavaScript (tracking, personalisation, chat widgets) worsens INP, and advertising banners or cookie layers that load later without reserved space ruin CLS. Anyone who works cleanly here improves SEO and conversion at the same time.
Typical causes of poor values and countermeasures
| Metric | Common cause | Countermeasure |
|---|---|---|
| LCP | Large, unoptimised images; slow server | Modern image formats (WebP/AVIF), lazy loading with priority for the LCP image, CDN, caching |
| INP | Too much blocking JavaScript | Split and defer scripts, remove unused code, break tasks into small chunks |
| CLS | Images/ads without fixed dimensions, fonts loaded late | Set width and height on media, reserve space for banners, preload fonts |
A concrete example
A typical Shopware scenario: a shop's home page shows a large hero banner. If this image is delivered as an uncompressed JPEG of several megabytes, LCP easily takes more than four seconds, which is "poor". If the same image is delivered as a correctly sized WebP via a CDN and given a high loading priority, LCP often falls below 2.5 seconds. If, in addition, a cookie banner slides in from the top after 800 milliseconds and pushes the content down, this shows up in CLS; if the space is reserved in advance instead, the layout remains stable. Such interventions are often manageable in effort but clearly measurable in effect.
How to measure the values
Several tools that complement each other are used for measurement: Google Search Console (the "Core Web Vitals" report, based on real field data), PageSpeed Insights (combines field and lab data), Lighthouse (lab data, integrated into Chrome) and the Chrome DevTools for detailed analysis. For ongoing monitoring, a look at Search Console is recommended, because it shows which groups of URLs miss Google's thresholds.
Common misconceptions
First: a perfect Lighthouse score of 100 does not automatically mean good Core Web Vitals; the field data of real users is decisive. Second: the Core Web Vitals are not a "mega ranking factor" that rescues poor content; they work as fine-tuning. Third, the myth persists that FID is still current; INP replaced FID in March 2024. Fourth: the thresholds are not binary "pass/fail" gates but guidance; Google evaluates the 75th percentile of user experiences.
Outlook
The Core Web Vitals are not a static construct. Google adjusts the metrics when new insights into user experience emerge; the change from FID to INP is the best example. For retailers this means: performance is not a one-off project but an ongoing task that has to be considered with every relaunch, every new tracking script and every theme update. The official, continuously updated reference is web.dev/vitals by Google.
FAQ
Which three metrics belong to the Core Web Vitals?
Largest Contentful Paint (LCP, perceived loading), Interaction to Next Paint (INP, responsiveness) and Cumulative Layout Shift (CLS, visual stability).
Are Core Web Vitals a ranking factor?
Yes, as part of the page experience signals since 2021. Their weight is moderate; they mainly work as a differentiator between pages of comparable relevance.
What does INP have to do with FID?
In March 2024, INP replaced First Input Delay (FID) as the Core Web Vital for responsiveness, because it captures the entire interaction behaviour and not just the first input.
Where can I see my Core Web Vitals?
Most reliably in Google Search Console (field data); additionally in PageSpeed Insights, Lighthouse and the Chrome DevTools.