Largest Contentful Paint Test
The Largest Contentful Paint Test measures the time from navigation start until the largest above-the-fold element renders — usually the hero image, hero text or main video poster. LCP is the most weighted Core Web Vital because it represents perceived load completion: when the LCP element appears, users feel the page has loaded. Google's "Good" threshold is 2.5 seconds; this tool measures your LCP, identifies the exact element, and lists the concrete optimizations to bring it down.
What This Tool Checks
- LCP timing in headless Chrome
- Identification of the LCP element (image, text, video)
- LCP element preload status
- Image format and size of LCP image
- fetchpriority="high" usage on LCP image
- Render-blocking resources delaying LCP
- Server response time (TTFB) contribution
Why It Matters for SEO
LCP is the most heavily weighted Core Web Vital in Google's page-experience signal. Pages with LCP over 4 seconds rank below otherwise identical pages with LCP under 2.5 seconds. LCP also correlates strongly with bounce rate and conversion — every second of LCP delay above 2.5s costs roughly 12% conversion. Fixing LCP usually means fixing the hero image: convert to WebP / AVIF, size it correctly, preload it with fetchpriority="high", and serve from a CDN.
How to Fix It
Identify your LCP element in this report. If it is an image: convert to WebP / AVIF, serve at the displayed dimensions, add fetchpriority="high" and a <link rel="preload">. Never lazy-load above-the-fold images. Inline critical CSS so nothing else blocks the hero render. Improve TTFB if it exceeds 600 ms.
How It Works
We measure LCP via the Performance Observer API, identify the element responsible (almost always the hero image or H1 wrapper), then audit the resource loading strategy for that element. The report tells you exactly which optimization will move LCP — preloading, format conversion, fetchpriority, or origin TTFB improvements.
Common Mistakes to Avoid
- Hero image in JPG / PNG format instead of WebP / AVIF
- Hero image lazy-loaded (delays LCP by hundreds of ms)
- Hero image with no fetchpriority="high" (deprioritised in queue)
- Render-blocking CSS / JS delaying the hero render
- Slow TTFB pushing LCP back regardless of frontend optimization
Quick Checklist
- LCP under 2.5 seconds
- LCP element preloaded with fetchpriority="high"
- LCP image in WebP or AVIF format
- No render-blocking CSS / JS above the LCP element
- TTFB under 600 ms