CORE WEB VITALS · SEO GLOSSARY

Largest Contentful Paint (LCP)

The Core Web Vital measuring how long it takes for the largest visible content element in the viewport to render — good LCP is under 2.5 seconds at the p75 threshold using real Chrome user data (CrUX).

Definition

Largest Contentful Paint (LCP) is a Core Web Vital introduced by Google in 2020 and incorporated into the Page Experience ranking signal in 2021. LCP measures the render time of the largest content element visible in the initial viewport — typically a hero image, an above-the-fold banner image, or (less commonly) a large text block such as the H1. The LCP element is identified by the browser: it tracks candidate elements as the page loads and updates the LCP mark each time a larger element renders, until the user first interacts with the page. Measurement is from the time the user navigates to the page (navigation start) to when the LCP element finishes rendering. **Thresholds (p75 from CrUX field data):** Good: ≤2.5s; Needs Improvement: 2.5s–4.0s; Poor: >4.0s. Google uses p75 CrUX data (the 75th percentile of real Chrome user measurements over a 28-day rolling window) for Page Experience ranking and the Core Web Vitals report in Google Search Console. Common LCP causes: server response time (slow TTFB adds directly to LCP); render-blocking resources (CSS/JS in `<head>` that delay the render tree); unoptimised LCP images (large files, no compression, no modern formats like WebP/AVIF); LCP images not preloaded with `<link rel="preload">` or `fetchpriority="high"`; client-side rendering of the LCP element (image only loads after JavaScript executes).

Why it matters for SEO

LCP is the Core Web Vital with the highest correlation to perceived page load speed and user experience. It directly affects the Page Experience ranking signal — pages with Poor LCP may be ranked below equivalent pages with Good LCP in competitive SERPs. LCP improvement also reduces bounce rates: studies consistently show bounce rate increases significantly after 3 seconds of load time. The most impactful LCP fix is almost always the LCP image: adding `fetchpriority="high"` to the hero image and ensuring it\'s in the initial HTML (not injected by JavaScript) can reduce LCP by 0.5–2 seconds on most sites.

How DeepSEOAnalysis checks this

DeepSEOAnalysis surfaces LCP from CrUX field data (p75, 28-day window) at URL level — the same data source Google Search Console uses, but per-URL rather than URL-group aggregated. The audit also detects LCP-related technical signals: whether the likely LCP element (hero image in the initial HTML) has fetchpriority="high", whether the LCP image is server-rendered vs client-injected (a critical distinction — client-injected LCP images cannot be preloaded), and whether render-blocking scripts in `<head>` precede the LCP element.

GLOSSARY

performance

Core Web Vitals

Three Google metrics — LCP, INP, and CLS — that measure real-user loading, interactivity, and visual stability.

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onpage seo

Above the Fold SEO

SEO considerations for content that appears without scrolling on initial page load — including LCP element placement, critical content prioritisation, and avoiding the Page Layout Algorithm penalty for ad-heavy above-fold areas.

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performance