The Core Web Vitals update explained: when page experience became a ranking factor

Fibvo editorial · 17 May 2023 · 6 min read

Rolled out gradually through June and August 2021, the Page Experience update formally made Core Web Vitals — a set of three specific measurements of loading speed, interactivity and visual stability — an official Google ranking signal for the first time. It was one of the most clearly defined, measurable updates Google has ever announced, in contrast to the far vaguer language used around content-quality updates.

The three original metrics

Core Web Vitals measures three specific aspects of how a page feels to actually use: how fast the main content loads, how quickly the page responds to interaction, and how much the layout shifts unexpectedly while loading. Each has its own threshold for 'good', 'needs improvement' and 'poor'.

• Largest Contentful Paint (LCP): how long the largest visible element takes to load — see our LCP guide.
• Cumulative Layout Shift (CLS): how much visible content shifts position unexpectedly — see our CLS guide.
• Interaction to Next Paint (INP), which replaced First Input Delay in 2024 as the responsiveness metric — see our INP guide.

Why it matters less than most SEOs assume, and more than most site owners assume

Google has repeatedly said Core Web Vitals is a relatively small ranking factor compared to content relevance and quality — a slow but genuinely excellent page will still usually out-rank a fast but thin one. But among sites of comparable content quality, page experience becomes the deciding factor, and a genuinely poor experience can also directly hurt conversion and bounce rate regardless of ranking impact.

Core Web Vitals rarely decides a ranking on its own — but it is often the tie-breaker between two pages that are otherwise equally relevant, and it always affects real users regardless of ranking.

What actually moves the scores

Unoptimised images, render-blocking JavaScript, third-party ad and tracking scripts, and web fonts loaded without proper fallback strategies are the most common causes of poor scores. Our page speed optimisation guide covers the specific fixes in more depth, but the short version is: reduce what has to load before the main content appears, and reserve space for elements that load asynchronously so nothing jumps around.

• Compress and properly size images — see our image compression guide.
• Defer non-critical JavaScript and third-party scripts.
• Reserve explicit space for ads, embeds and images before they load, to prevent layout shift.
• Use a CDN to reduce latency for visitors far from your server, covered in our CDN and SEO guide.

Measuring your own scores

Google Search Console's Core Web Vitals report shows real, field-collected data from actual visitors, which is more representative than lab tests alone. Google's own web.dev Vitals guide is the authoritative technical reference for thresholds and measurement methodology.

Frequently asked questions

If your Core Web Vitals scores need work and you are not sure where to start, get in touch — this is one of the more mechanical, fixable parts of SEO and usually does not need a full redesign.

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Written by Fibvo — Bengaluru and Erode, India — working with clients in other time zones. Questions, or think we have it wrong? Tell us.