Core Web Vitals
Core Web Vitals are Google three metrics for loading, interactivity, and visual stability. Learn the thresholds and how much they affect rankings.
TL;DR
Core Web Vitals are three metrics Google uses to quantify user experience: how quickly the main content loads, how fast the page responds to input, and how much the layout shifts while loading. They are measured from real visits rather than laboratory simulations. The current set is LCP, INP and CLS, with INP having replaced the older First Input Delay metric.
Why Core Web Vitals matter
They are the closest thing to an objective measure of whether a page feels usable, and the only user-experience signals Google publishes thresholds for.
- Ranking input: A small factor, used mainly as a tiebreaker between pages of comparable relevance.
- Real-user data: Scores come from actual Chrome visits, so they reflect real devices and networks rather than a test environment.
- Conversion correlation: Slow and unstable pages lose users before content loads, independent of any search consideration.
- Crawl efficiency: Faster server responses raise crawl rate limits, which affects how much of a large site gets fetched.
The three metrics
Largest Contentful Paint (LCP)
How long until the largest visible element renders. Good is 2.5 seconds or less, measured at the 75th percentile of visits.
Interaction to Next Paint (INP)
How quickly the page responds visually after a user interacts. Good is 200 milliseconds or less.
Cumulative Layout Shift (CLS)
How much visible content moves unexpectedly during loading. Good is 0.1 or less.
The 75th percentile rule
Scores are assessed at the 75th percentile, so a quarter of your visitors can have a worse experience and the page still passes.
Field data over lab data
Real user measurements decide your assessment. Lab tools diagnose causes but do not determine the score.
Per-URL and per-group
Google evaluates individual URLs where it has enough data and falls back to grouping similar pages when it does not.
Core Web Vitals vs. page speed
Core Web Vitals: Three specific metrics with published thresholds, measured from real visits, tied to what a user perceives.
Page speed: A broader informal idea covering load time, file sizes and server response, often measured in the lab.
Vitals are a subset of page speed chosen because they correlate with perceived experience. A page can post a fast total load time and still fail CLS if elements jump around while loading.
Performance is one input among many in whether pages get crawled, indexed and cited. Findrix runs a 31-point technical audit covering rendering and crawler access, then tracks how often seven AI engines cite you against named competitors. Every gap comes with the fix already written: technical, content and off-site. The audit is free, takes about a minute, and requires no signup.
Common causes of poor scores
- Unoptimised hero images: The most frequent LCP problem, and usually the easiest to fix.
- Heavy JavaScript: Long tasks block the main thread and wreck INP.
- Images without dimensions: Content reflows when they load, which drives CLS.
- Injected banners and ads: Elements appearing above existing content push everything down.
- Slow server response: A high time to first byte caps LCP no matter how well the front end is built.
- Web fonts: Text swapping fonts mid-load shifts layout and hurts CLS.
How much they actually matter for ranking
Less than the volume of writing about them implies. Google has been consistent that Core Web Vitals are a minor signal, used to separate pages that are otherwise similarly relevant. No page has ever outranked a substantially better answer by loading faster.
That framing gets teams into trouble in both directions. Some ignore performance entirely because it is only a small ranking factor, missing that slow pages lose conversions regardless of rank. Others spend a quarter chasing a perfect score on pages nobody visits.
Fix genuinely poor scores on pages that matter commercially, and stop there. Failing to passing is worth having; passing to perfect rarely is.
Frequently asked questions
Are Core Web Vitals a ranking factor?
Yes, and a small one. Google describes them as part of page experience signals, useful mainly as a tiebreaker between pages of similar relevance. Content quality remains far more influential.
What replaced First Input Delay?
INP, Interaction to Next Paint, became the official responsiveness metric in March 2024. FID measured only the delay before the first interaction was processed, which missed sluggishness later in a session.
Do Core Web Vitals affect AI search visibility?
Not directly. AI engines care about whether they can fetch and parse your content. Performance matters indirectly, since slow servers reduce crawl rates and unrendered content cannot be cited.