Since 2021, Google uses three numbers to evaluate the quality of your website and decide where to show it in search results. If your site loads slowly, elements shift around during loading, or it responds sluggishly to clicks — you lose rankings, even if your content is excellent.
What Are Core Web Vitals
Three metrics Google measures on every page:
LCP — Largest Contentful Paint is the loading time of the largest visible element on the page — usually a hero image or main headline. Target: under 2.5 seconds. Above 4 seconds — red zone.
CLS — Cumulative Layout Shift measures whether elements move around during page loading. Classic example: you click a button, but just before clicking the page shifts and you hit an ad instead. Target: below 0.1. Above 0.25 — red zone.
INP — Interaction to Next Paint is the time from a click or keypress to a visible response from the page. It replaced FID in March 2024. Target: under 200ms. Above 500ms — red zone.
Why Wix and WordPress Sites Score Poorly
Wix and WordPress generate pages with large amounts of JavaScript and CSS loaded synchronously. Every installed WordPress plugin adds its own scripts — 20 plugins often means 20 separate JS files loaded before the page renders. Result: LCP of 5–8 seconds on slower connections.
Wix additionally renders pages through its own engine which generates heavy HTML. Wix sites regularly score 40–60 in Lighthouse Performance — well below the 90+ target.
Next.js, on the other hand, statically compiles pages, splits code into smaller chunks and loads only what's needed for the current page. Images are automatically converted to AVIF/WebP. Result: LCP under 2 seconds in a standard configuration.
How to Check Your Core Web Vitals
Two tools worth knowing:
PageSpeed Insights (pagespeed.web.dev) — enter a URL and get results for mobile and desktop. Shows both lab data (simulation) and real user data from Chrome (CrUX). Free, no registration.
Google Search Console → Core Web Vitals section — shows how Google evaluates your pages based on real user data from the past 28 days. Available only if you have verified ownership in GSC.
Chrome DevTools Lighthouse (F12 → Lighthouse) also works, but only measures on your device — results may differ from what Google sees.
How to Improve Your Scores
Most common causes of poor results and concrete fixes:
Slow LCP: Uncompressed images are the number one culprit. Switch JPG/PNG to AVIF or WebP — file size drops 60–80% with no visible quality difference. Add loading="lazy" to below-the-fold images. The hero image should have priority (Next.js) or fetchpriority="high" (vanilla HTML).
High CLS: Always specify image dimensions (width and height) so the browser reserves space before loading. Avoid injecting ads and banners that push content down.
Poor INP: Limit JavaScript executing on the main thread. Every heavy scroll or mousemove listener without debounce can block response to clicks.
Render-blocking fonts: Add font-display: swap to all custom fonts. Next.js does this automatically when using next/font.
Frequently Asked Questions
What is LCP and what score is good?
LCP (Largest Contentful Paint) is the loading time of the largest visible element on the page — usually an image or main headline. A good score is under 2.5 seconds. Between 2.5 and 4 seconds is the warning zone, above 4 seconds — Google considers the page slow.
Why does a Wix site have poor Core Web Vitals?
Wix generates heavy HTML and loads large amounts of JavaScript needed for its editor. End users download this code even if they don't need it. Wix sites regularly score Lighthouse Performance 40–60 instead of the required 90+.
How do I check my site's Core Web Vitals?
Go to pagespeed.web.dev and enter your site address. You'll get results for mobile and desktop with specific suggestions on what to improve. If you have Google Search Console — the Core Web Vitals section shows how Google rates your pages based on real user data.
Do Core Web Vitals affect Google rankings?
Yes — since May 2021, Core Web Vitals are an official ranking factor. Google confirms that with comparable content and links, a site with better CWV can rank higher. The biggest effect is seen when two pages have similar content quality — then speed can tip the balance.
How do I improve INP on a WordPress site?
Start by disabling plugins that add JavaScript on every page (counters, chatbots, popups). Use Query Monitor to see which plugins load the most scripts. Minimize the number of plugins. If you use a page builder (Elementor, Divi) — consider switching to a lighter theme or rebuilding without a page builder.
