Glossaire · SEO

LCP (Largest Contentful Paint)

LCP (Largest Contentful Paint) is the Core Web Vitals metric from Google that measures the time it takes to render the largest visible element within the browser viewport, usually a hero image, a video, or a large block of text. Expressed in seconds, it marks the moment users perceive that the page has loaded its main content. Google considers an LCP of 2.5 seconds or less as good, between 2.5 and 4 seconds as needs improvement, and above 4 seconds as poor. Measured at the 75th percentile of real user visits, LCP has been an official ranking signal since Core Web Vitals were integrated into the algorithm. A fast LCP improves perceived experience, lowers bounce rate, and sends a strong technical quality signal to both search engines and AI models that favor the performance of the sources they cite.

LCP is one of the three Core Web Vitals that Google uses to assess the technical quality of a page. Unlike older purely technical speed metrics, it focuses on what users actually perceive: the moment the main content becomes visible on screen.

How it works

The browser monitors elements shown within the visible viewport and continuously identifies the largest one. That element is often a hero image, a banner, a video poster, or a large block of text. LCP records the moment this largest element finishes rendering. Measurement stops as soon as the user interacts with the page.

Google calculates your score at the 75th percentile of real page loads: in other words, 75% of your visitors must reach an LCP at least as good as the target threshold.

How to improve your LCP

The most effective levers act upstream of rendering:

Reduce TTFB by optimizing the server, caching, and CDN.
Compress and properly size the hero image, serving it as WebP or AVIF.
Preload the LCP element with a preload tag.
Eliminate render-blocking resources (CSS and JavaScript) above the fold.
Avoid lazy-loading the main image.

Key takeaway

LCP does not measure raw speed but perceived comfort: optimize the most visible element on screen first, not the entire page.

Why it matters

A fast LCP improves user experience, lowers bounce rate, and is an official ranking signal. Beyond classic SEO, answer engines and generative AI favor technically reliable sources: a slow page sends a lower quality signal. Optimizing LCP therefore strengthens both your search ranking and your citability by AI.

FAQ

Questions fréquentes

An LCP of 2.5 seconds or less is considered good by Google. Between 2.5 and 4 seconds, the page needs improvement. Beyond 4 seconds, the LCP is rated poor and hurts the user experience.

You can measure LCP with PageSpeed Insights, Lighthouse, or the Core Web Vitals report in Search Console. Field data (CrUX) reflects the real experience of your visitors over a 28-day window.

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