Development
FundamentalsCore Web Vitals: What Google Measures on Your Website and Why It Costs Revenue
Core Web Vitals are Google's yardstick for loading speed, responsiveness, and stability of a website. What LCP, INP, and CLS mean, which thresholds apply, and how to improve the scores concretely.
of Josef Kujawski6 min read
Short answer
Core Web Vitals are Google's three metrics for the technical experience of a website: LCP measures when the main content has loaded (good: up to 2.5 seconds), INP how fast the page reacts to input (good: up to 200 milliseconds), and CLS whether content jumps while loading (good: up to 0.1). What counts is the real user data of the last 28 days, not lab tests. The scores are a ranking factor and a revenue question, because every second of loading time costs visitors. The most important levers are optimized hero images, cleaned-up scripts, and fixed size attributes for all embeds.
The Problem: Your Website Feels Fine, but Google Measures Something Else
On your office computer the website loads quickly. Still, the tools show red values, rankings slowly decline, and nobody can say exactly why. The reason: Google does not measure how your website feels to you, but how it performs for real visitors on real devices.
This measurement has a name: Core Web Vitals.
The Principle: Three Metrics for the User Experience
In 2020, Google defined three metrics with the Core Web Vitals that summarize the technical experience of a page. [1] They are part of the ranking signals and measure three different questions:
- LCP (Largest Contentful Paint): when is the main content there? It measures when the largest visible element, usually the hero image or the headline, has fully loaded. Good is up to 2.5 seconds.
- INP (Interaction to Next Paint): how fast does the page react? It measures the delay between an input, such as a click, and the visible reaction. Good is up to 200 milliseconds. INP replaced the older FID metric in March 2024. [2]
- CLS (Cumulative Layout Shift): does the page jump while loading? It measures how much content shifts during loading, for example when an image loads late and pushes the text away. Good is a value up to 0.1.
Crucially: Google does not evaluate lab tests but the real user data of the last 28 days, the so-called field data. A page passes when at least 75 percent of visits meet all three thresholds. [1]
Origin and Context
The Core Web Vitals are part of Google's page experience initiative, with which the search engine wanted to make technical quality measurable instead of merely recommending it. The thresholds are deliberately strict: they are based on what users perceive as "instant", not on what is technically convenient to achieve.
Context matters: Core Web Vitals are one ranking factor among many, and content beats technology. But with comparable content, technical quality helps decide, and independent of ranking, every second of loading time provably costs visitors and revenue. [3]
Applying It to Your Website
- Improve LCP: the hero image is almost always the bottleneck. Modern formats, the right resolution per device, preloading the most important image, and a fast server or cache bring the biggest jumps.
- Improve INP: heavy scripts block responsiveness. Fewer tracking scripts, split and deferred JavaScript, and lean animations make the page snappy again.
- Improve CLS: every image and every embed needs a fixed size attribute so the text does not jump. Banners and cookie notices inserted afterwards are classic culprits.
- Measure with real data: PageSpeed Insights shows field data from real users per URL, Search Console aggregates it for the whole website. A lab test alone is not enough.
Kernaussage
Core Web Vitals are not a developer topic but a revenue question: they decide how many visitors get to see your content at all before they leave impatiently. The good news: all three values can be measured and improved deliberately.
The Solution: Measure, Prioritize, Keep at It
Here is how to proceed:
- Measure the status quo with field data. PageSpeed Insights and Search Console show which pages break the thresholds and on which of the three values.
- Start with the biggest lever. In most cases that is LCP and therefore the hero image: shrink it, use a modern format, preload it.
- Clean up the scripts. Every tracking and marketing script costs responsiveness. What does not measurably bring revenue gets removed or deferred.
- Secure the values permanently. Every new feature and every new image can worsen the scores again. Regular checks belong to maintenance, not to the relaunch.
| Metric | Question | Good | Typical cause of bad scores |
|---|---|---|---|
| LCP | When is the main content there? | up to 2.5 s | Huge hero images, slow server |
| INP | How fast does the page react? | up to 200 ms | Heavy scripts, too much tracking |
| CLS | Does the page jump while loading? | up to 0.1 | Images without size attributes, late banners |
The Maluure Approach
We treat performance as part of the design, not as afterwork. That is why we measure our own pages and those of our clients regularly with real user data, and we build hero images, fonts, and scripts from the start so the thresholds are met with room to spare. A beautiful page nobody gets to see is not a beautiful page.
Performance is the rudest form of design: it decides whether anyone gets to see your work at all. That is why for us it is not an item on the acceptance list but a criterion from the first draft.
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Frequently asked questions
What are Core Web Vitals?+
Three metrics defined by Google for the technical user experience of a website: LCP for the loading time of the main content, INP for the responsiveness to input, and CLS for visual stability while loading. They are part of the ranking signals.
Which thresholds apply to Core Web Vitals?+
LCP up to 2.5 seconds, INP up to 200 milliseconds, and CLS up to 0.1. A page passes when at least 75 percent of real visits meet all three thresholds.
What is the difference between INP and FID?+
FID only measured the delay of the first input. INP, the official metric since March 2024, looks at response time across the entire visit and is therefore much more meaningful.
How do I measure my Core Web Vitals?+
With PageSpeed Insights for individual pages and with Search Console for the whole website. What matters is the field data from real users over the last 28 days, not just the lab test.
Are Core Web Vitals a ranking factor?+
Yes, they are part of Google's ranking signals, but one among many. Good content beats good technology, but with comparable content, technical quality helps decide. Independent of ranking, every second of loading time costs visitors and revenue.
How do I improve LCP?+
Almost always through the hero image: modern image formats, the right resolution per device, preloading the most important image, and a fast server or cache bring the biggest improvements.
What causes a bad CLS score?+
Above all images and embeds without fixed size attributes, banners inserted afterwards, cookie notices, and fonts that shift the text when they load.
Sources
- Google: Web Vitals. Definition, Grenzwerte und Messung, web.dev (2020)
- Google: INP wird offizieller Core Web Vital und ersetzt FID, web.dev (2024)
- Google: Why Speed Matters. Auswirkungen von Ladezeit auf Absprungraten, web.dev (2020)
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Author
Josef KujawskiManaging Director & Creative Director at Maluure
Josef leads the strategic and creative development of brands at Maluure. For over a decade, he has guided medium-sized businesses from brand positioning to digital delivery.
Managing Director of Maluure GmbH, Cologne. Specialising in corporate design, brand strategy and digital brand experiences.
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