What are Core Web Vitals? LCP, INP and CLS explained

Core Web Vitals are three metrics Google uses to measure the real-world experience of a web page: Largest Contentful Paint (LCP) for loading, Interaction to Next Paint (INP) for interactivity, and Cumulative Layout Shift (CLS) for visual stability.

The three metrics and their thresholds

According to web.dev, a page gives a good user experience when:

  • LCP (loading) occurs within 2.5 seconds of when the page first starts loading;
  • INP (interactivity) is 200 milliseconds or less;
  • CLS (visual stability) is 0.1 or less.

INP became a Core Web Vital in March 2024, replacing First Input Delay (FID).

How a page passes

The recommended measurement is the 75th percentile of page loads, segmented into mobile and desktop. A page passes only if it meets the target at the 75th percentile for all three metrics. Using the 75th percentile means at least three out of four visits have to be good, not just the average visit.

Worked example

Suppose a hypothetical product page has, at the 75th percentile, an LCP of 2.1 seconds on desktop and 3.4 seconds on mobile, with INP and CLS within their targets on both. It passes on desktop but fails on mobile, because mobile LCP is above 2.5 seconds. Fixing the slow hero image on mobile would be the priority.

Why it matters for an online store

Google Search Central recommends that site owners achieve good Core Web Vitals “for success with Search,” and says this, along with other page experience aspects, aligns with what its core ranking systems seek to reward. Beyond search, the same metrics describe what shoppers feel: a slow main image, a tap that does not respond, or a button that jumps just as someone tries to click it. You can see how your pages perform in the Core Web Vitals report in Google Search Console.

Common mistakes

  • Treating a lab score as the result. A lab test in one browser is useful for debugging, but Core Web Vitals are assessed on real-user data across many visits and devices.
  • Optimizing only the homepage. Shoppers often land directly on product and category pages, so those templates need the same attention.
  • Ignoring mobile. Mobile and desktop are assessed separately, so a fast desktop page can still fail on phones.
  • Layout shifts from late content. Images without reserved space, banners and embeds that load late push content around and raise CLS.

CIQRA pages are built on the server and served from a global edge network, and images are resized and converted to AVIF and WebP automatically.

Related terms

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