Wat is LCP (Largest Contentful Paint)?
Snelle definitie
LCP meet de tijd die nodig is voor het grootste zichtbare contentelement op een pagina, zoals een hero-afbeelding of een koptekst, om volledig te worden weergegeven.
Largest Contentful Paint (LCP) is one of Google's three Core Web Vitals. It measures the render time of the largest image, video, or block of text visible in the viewport when the page first loads. In practical terms, it measures when the main content of a page becomes visible to the user.
Google defines good LCP as under 2.5 seconds, needs improvement between 2.5-4 seconds, and poor above 4 seconds. These thresholds are measured at the 75th percentile of page loads across real users.
The "largest" element is typically the hero image on a landing page, the featured image on a blog post, a large heading, or a video thumbnail. The browser automatically identifies which element is the largest in the initial viewport. As the page loads, the LCP element might change (for example, from a heading to a hero image that loads later).
Common causes of poor LCP include slow server response time (high TTFB), render-blocking JavaScript and CSS, slow resource loading (unoptimized images, missing image dimensions), and client-side rendering that delays content visibility. Optimization strategies include using a CDN, preloading critical resources, optimizing images (using modern formats like WebP/AVIF and appropriate sizing), and eliminating render-blocking resources.
Waarom het belangrijk is
LCP is the most important loading metric because it measures when users see the content they came for. A fast LCP means users quickly confirm they're on the right page and start consuming content. A slow LCP means users stare at a blank or partially loaded page, and many will abandon before it finishes.
Since LCP is a Google ranking factor, improving it can directly boost your search visibility. It's also the metric most strongly correlated with user satisfaction and engagement.
Praktijkvoorbeelden
A travel website optimized their hero images by serving WebP format and appropriate sizes, reducing LCP from 5.2 seconds to 1.9 seconds on mobile
A blog preloaded their LCP element (a featured image) and saw LCP improve from 3.1s to 1.6s, resulting in a measurable decrease in bounce rate
An e-commerce site discovered that a large CSS file was render-blocking their LCP element; inlining critical CSS brought LCP from 4.0s to 2.1s
A news site implemented responsive images with the srcset attribute, serving smaller images to mobile devices and reducing mobile LCP by 40%
Gerelateerde termen
Core Web Vitals
Core Web Vitals zijn drie specifieke statistieken van Google die de werkelijke gebruikerservaring op websites meten: laadprestaties (LCP), interactiviteit (INP) en visuele stabiliteit (CLS).
CLS (Cumulative Layout Shift)
CLS meet de totale hoeveelheid onverwachte layoutverschuivingen die optreden tijdens de volledige levenscyclus van een pagina, en kwantificeert hoeveel zichtbare inhoud beweegt.
TTFB (Time to First Byte)
TTFB meet de tijd van het moment dat een browser een pagina aanvraagt totdat het de eerste byte aan gegevens van de server ontvangt, als indicator van serverrespons.
CDN (Content Delivery Network)
Een CDN is een netwerk van geografisch verspreide servers die webinhoud aan gebruikers levert vanaf de server die het dichtst bij hen staat, waardoor laadtijden worden verkort.
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