Lighthouse simulates a visit under ideal (or degraded) laboratory conditions ('Lab Data'), which is useful for debugging but does not reflect reality. CrUX (Chrome UX Report) gathers data from REAL users ('Field Data') browsing your site. It is the only metric Google uses for its SEO ranking (Core Web Vitals).

Since Google's 'Page Experience' update, Core Web Vitals (LCP, INP, CLS) have become an official ranking factor. A slow or unstable site will be penalized in search results, especially on mobile. Optimizing your core web vitals is therefore essential to maintain and improve your SEO positions.

A one-off audit is not enough. Site updates, adding marketing tags, or browser changes can degrade your stats. We recommend implementing continuous monitoring via the CrUX API connected to a Dashboard (Looker Studio), coupled with an alerting system to react immediately in case of regression.

It's classic! You probably test with a fiber connection and a powerful computer (MacBook Pro). Your users might have mid-range phones and unstable 4G. Google judges your site on the experience of ALL your visitors (the 75th percentile of CrUX data). That's why optimization must target the real user, not the developer.

INP replaced FID (First Input Delay) in March 2024. It measures the overall responsiveness of your page to all interactions (clicks, taps, key presses). A poor INP score means your site 'freezes' or takes time to react when the user clicks, creating major frustration and increasing bounce rates.

GTM itself is very lightweight, but the tags it fires can be heavy! If you load 50 third-party scripts (hotjar, chat, FB pixels...) at page start, your performance will drop. We optimize tag firing (smart triggers, prioritization) and migrate what is possible to Server-Side (sGTM) to lighten the user's browser.

Yes, a critical role. If your server takes 1 second to respond (TTFB), even the most optimized code won't save your LCP. Using a CDN (like Cloudflare) allows serving your resources (images, CSS, JS) from a server close to the user, reducing latency. We also audit your infrastructure to ensure compression (Brotli/Gzip) and cache management are optimal.

LCP (Largest Contentful Paint) measures SPEED: when does the main element of the page (image, title) display? CLS (Cumulative Layout Shift) measures STABILITY: does the page move during loading (buttons jumping, text shifting)? Both are essential: one for waiting, the other for frustration.