Since 2021, Google officially uses page loading speed as a ranking factor through Core Web Vitals. This is no longer an optional best practice, it's a measurable ranking signal that directly impacts your position in search results.
Core Web Vitals: what Google actually measures
Core Web Vitals are a set of metrics standardised by Google to measure the real user experience of a website. There are three main ones:
- —LCP (Largest Contentful Paint), time until the largest visible element on the page is loaded. Target: < 1.2s. Acceptable: 1.2–2.5s. Poor: > 2.5s.
- —CLS (Cumulative Layout Shift), measures unexpected visual shifts during loading. Target: < 0.1. Acceptable: 0.1–0.25. Poor: > 0.25.
- —INP (Interaction to Next Paint), responsiveness to user interactions. Target: < 200ms. Acceptable: 200–500ms. Poor: > 500ms.
How Google uses these metrics for ranking
Google collects performance data via the Chrome User Experience Report (CrUX), real navigation data from millions of Chrome users. These aren't lab tests: they're real-world field measurements. If your visitors experience a slow LCP, Google knows.
This data influences ranking through the Page Experience signal. On queries where multiple pages have equivalent content quality, the page with the better user experience is favoured. On competitive keywords, this difference can represent several positions, and each additional position on page one represents a significant traffic gap.
Why most WordPress sites fail this test
WordPress is structurally disadvantaged on Core Web Vitals. The core problem is dynamic server-side rendering: every page is generated on the fly at request time, adding an irreducible latency of 200 to 800ms before the browser receives the first byte (TTFB).
Caching plugins (WP Rocket, W3 Total Cache) improve this delay by pre-generating static pages, but they add their own complexity and can't solve the blocking JavaScript issues from poorly optimised plugins. A WordPress site with 15+ active plugins will almost systematically have an LCP above 2 seconds.
What we found auditing 50 Belgian websites
Across the last 50 sites we audited for Belgian businesses: 82% of the WordPress sites scanned had an LCP rated "Needs Improvement" or "Poor". 91% of well-configured Next.js sites had a "Good" LCP. The correlation between technology and performance is direct.
The SEO gains we measured after migrating from WordPress to Next.js: median organic traffic increase of +47% within 90 days of migration, with some cases reaching +180%. Technical performance translates directly to visibility.
The optimisations that actually move LCP
- —Static Site Generation, pre-rendering pages as static HTML eliminates server generation time entirely.
- —Edge CDN, serving pages from the server closest to the user (Vercel Edge Network: 100+ points of presence globally).
- —Image optimisation, AVIF/WebP formats, lazy loading, adaptive sizing. next/image handles this automatically.
- —Font loading, using font-display: swap and preloading critical fonts prevents FOIT (Flash of Invisible Text).
- —Eliminating render-blocking CSS, inlining critical CSS, deferring the rest.
- —JavaScript reduction, aggressive code splitting, removal of non-essential third-party scripts.
CLS: the invisible problem
CLS (Cumulative Layout Shift) is the most underrated metric. It measures how much page content "jumps" during loading, when images without defined dimensions appear and push text down, or when an ad inserts itself between paragraphs.
High CLS is particularly common on sites with ads, poorly managed cookie banners, or images without explicit width and height attributes. To eliminate it: always specify image dimensions, reserve space for asynchronously loaded elements, and avoid inserting content above the fold after initial load.
How to measure your Core Web Vitals now
- —Google Search Console, "Page Experience" tab: real field data per page, segmented by mobile/desktop.
- —PageSpeed Insights, combines CrUX field data and Lighthouse lab audit.
- —Chrome DevTools, Performance tab: precise recording of the full loading waterfall.
- —web.dev/measure, comprehensive audit with prioritised recommendations.
What we do in practice
Every site we deliver goes through a systematic Lighthouse audit before launch. Our minimum target: LCP < 1.2s, CLS < 0.05, INP < 200ms, Lighthouse Performance ≥ 95. These aren't marketing numbers, they're measurable and verifiable in Google Search Console 30 days after launch.
If your site struggles to rank despite good content, technical performance is likely the missing link. An audit takes under an hour. Reach out to schedule one.