Core Web Vitals are a set of standardised metrics that measure real-world user experience of a web page's loading, interactivity and visual stability.
Definition
Core Web Vitals are a set of standardised metrics that measure real-world user experience of a web page's loading, interactivity and visual stability. The current three are Largest Contentful Paint (LCP, how long until the main content renders), Interaction to Next Paint (INP, how responsive the page is to user input), and Cumulative Layout Shift (CLS, how much the layout jumps around during load).
Each has a "good" threshold, and the metrics are measured from actual visits, not lab tests.
Core Web Vitals are part of the broader page-experience signal search engines use in ranking. Their direct ranking weight is modest — great content on a slightly slow page still outranks thin content on a fast one — but they act as a tiebreaker between comparable pages, and poor scores hurt conversion and engagement regardless of ranking effect.
In context
On iGaming affiliate sites, Core Web Vitals problems come from predictable sources: large unoptimised operator logos and screenshots hurting LCP, heavy third-party scripts (ad and affiliate tags, consent managers, analytics, chat widgets) delaying interactivity and INP, and content that loads in above the fold — cookie banners, sticky bonus bars, lazy-loaded images without reserved space — causing layout shift and a poor CLS. Comparison tables that build client-side and reflow the page are a common CLS and INP offender.
Improving the scores is mostly disciplined front-end work: serve appropriately sized, modern-format images with explicit dimensions; defer or lazy-load non-critical scripts and load third-party tags with care; inline critical CSS and avoid render-blocking resources; and reserve space for any element that loads in after the initial paint so nothing jumps. Because the metrics are measured from real users, improvements show up in field data over about a month rather than immediately.
The practical target is to clear the "good" thresholds for the majority of visits, which removes Core Web Vitals as a competitive disadvantage and improves the conversion rate of every visit at the same time.
Worked example
An affiliate's field data shows failing LCP (4.1s) and CLS (0.28) on mobile, mostly from oversized screenshots and a bonus bar that pushes content down after load. It compresses and dimensions the images, reserves space for the bonus bar, and defers the chat widget.
Field LCP falls to 2.3s, CLS to 0.04, and mobile conversion rises 9%.
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