PERFORMANCE · SEO GLOSSARY
LCP Image
The image element identified by Chrome as the Largest Contentful Paint (LCP) candidate on a page — the largest visible image in the initial viewport that determines the LCP timing score, typically the hero image, product thumbnail, or featured photo at the top of the page.
Definition
The LCP image is the specific image element that the browser identifies as the Largest Contentful Paint element on a given web page — the image that is both the largest by rendered area and visible in the initial viewport at the time of the LCP measurement. Understanding which element is the LCP candidate is essential for targeted optimisation. LCP element types: the LCP element can be an image (`<img>`), a CSS background image set on a block element, a video poster image, or a text block — but on the vast majority of commercial websites, the hero image, product thumbnail, or page banner is the LCP element. Why the LCP image matters for SEO: (1) LCP is the most directly impactful Core Web Vitals metric for user experience — it measures when the main content appears to the user. (2) Poor LCP (>4s p75 CrUX) triggers a "Poor" page experience signal; Good LCP (≤2.5s) is the target. (3) The LCP image is typically the largest single optimisation target for LCP improvement. LCP image optimisation checklist: (1) Serve in WebP or AVIF format — smallest possible file size. (2) Serve at the exact display dimensions — not a larger image scaled down in CSS. (3) Include a `<link rel="preload" as="image">` in the `<head>` — starts downloading before the browser discovers the image in the HTML. (4) Use `loading="eager"` (or omit the loading attribute) — never `loading="lazy"` on the LCP element. (5) Serve from a CDN with edge locations near users. (6) Use correct `fetchpriority="high"` attribute on the `<img>` tag — signals browser priority for downloading this image. (7) For responsive images, use `srcset` with the correctly sized image for each viewport width.
Why it matters for SEO
The LCP image is the single most impactful performance optimisation target for most websites. Improving the LCP image\'s loading time (through format optimisation, preloading, lazy-loading removal, CDN delivery, and correct sizing) is the most direct path to improving LCP CrUX scores — and therefore the page experience ranking signal and user abandonment rates. Identifying which element is the LCP and specifically optimising it is the foundation of any Core Web Vitals improvement program.
How DeepSEOAnalysis checks this
DeepSEOAnalysis identifies the LCP element on audited pages and checks for the full set of LCP image optimisations: WebP/AVIF format, `<link rel="preload">` presence, absence of `loading="lazy"`, `fetchpriority="high"` attribute, and correct sizing relative to display dimensions. CrUX LCP field data at p75 from real Chrome users provides the real-world performance measurement. Pages with poor CrUX LCP and an unoptimised LCP image have a clear, specific optimisation path.
GLOSSARY
Related terms
performance
WebP (SEO)
The WebP image format developed by Google — offering significantly smaller file sizes than JPEG and PNG at equivalent visual quality — which improves page loading performance (LCP in particular) and is supported by all modern browsers, making it the recommended image format for web images.
Read definition →performance
AVIF (SEO)
The AVIF (AV1 Image File Format) image format — offering even better compression than WebP (typically 20–50% smaller at equivalent quality) — which improves LCP and page performance but has less complete browser support than WebP, typically requiring a fallback strategy using the `<picture>` element.
Read definition →performance
Image Compression (SEO)
The process of reducing image file sizes through lossy or lossless compression algorithms — directly impacting page load speed, LCP times, and Core Web Vitals — and the SEO implications of image compression choices for page performance and ranking.
Read definition →performance
Lazy Loading SEO
The SEO implications of lazy loading — deferring loading of images and other resources until they enter the viewport — which improves initial page load performance but can harm LCP if the main content image is lazy-loaded, and can prevent off-screen content from being indexed if text content is lazy-loaded.
Read definition →performance
Preconnect (SEO)
The `<link rel="preconnect">` resource hint that instructs the browser to establish a TCP+TLS connection to a specified origin in advance of it being needed — reducing latency for third-party resources (fonts, CDN assets, analytics) that would otherwise wait for connection establishment when first requested.
Read definition →See how your site scores on LCP Image.
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