LCP: definition, thresholds and optimisation
Updated on February 22, 2026
Quick definition
LCP (Largest Contentful Paint) is a Core Web Vitals metric that measures the time required for the largest content element visible in the viewport to be rendered on screen. LCP is considered good if under 2.5 seconds, needs improvement between 2.5 and 4 seconds, and poor beyond 4 seconds. It is the primary indicator of perceived loading speed according to Google.
How it works
LCP identifies the largest visible element in the viewport at page load — typically a hero image, product photo, text block or video — and measures the delay between the start of loading and the moment that element is fully displayed.
The official Google thresholds are:
- Good (green): under 2.5 seconds
- Needs improvement (orange): between 2.5 and 4 seconds
- Poor (red): beyond 4 seconds
The main causes of poor LCP are:
- Images that are too heavy or not preloaded
- Render-blocking CSS and JavaScript resources
- High server-side TTFB from a slow server
- Absence of effective caching
Google estimates that a one-second LCP improvement can boost mobile conversions by 8%.
Why it matters
LCP is the most important Core Web Vitals metric for perceived experience, as it corresponds to the moment the user judges the page is 'loaded'.
An LCP above 4 seconds drives significantly higher abandonment rates. LCP is also one of the three official Google ranking signals since 2021, making it a direct SEO lever.
How to improve or use it
- 1Preload the hero image with `<link rel="preload">` and the `fetchpriority="high"` attribute.
- 2Compress your images and convert them to WebP or AVIF.
- 3Configure a CDN to reduce network latency.
- 4Optimise your TTFB by enabling server-side caching.
- 5Avoid blocking scripts before the main content by loading them asynchronously.
- 6Regularly audit your LCP scores via PageSpeed Insights on real-world field data.
With Sublim
Sublim monitors your pages' loading performance under real conditions, directly in your analytics dashboard. By correlating LCP per page with bounce and conversion rates, you quickly identify which slow pages cost you customers — cookieless, hosted in Europe, in full GDPR compliance.
Frequently asked questions
Which HTML elements can be a page's LCP?
LCP is measured on the following elements: `<img>` tags, images inside `<svg>` tags, images loaded via the CSS `background-image` property, text blocks (`<p>`, `<h1>`, etc.) and video elements (`<video>` with poster). Google ignores elements with low opacity or a size below 0.15% of the visible area.
What is the difference between LCP and FCP?
FCP (First Contentful Paint) measures when the first content element (text or image) appears on screen, while LCP measures when the largest visible element is rendered. LCP is considered more representative of perceived experience because it corresponds to the user's perception of 'fully loaded'.
Does LCP improve with faster hosting?
Yes, the server's TTFB (Time To First Byte) directly affects LCP. High-performance hosting with low network latency and server-side caching can shave several hundred milliseconds off LCP. However, image size and blocking resources often remain the main causes of poor LCP.
Related terms
Core Web Vitals are a set of three metrics defined by Google to object…
INP (Interaction to Next Paint) is the [Core Web Vitals](core-web-vita…
CLS (Cumulative Layout Shift) is a [Core Web Vitals](core-web-vitals) …
The bounce rate is the percentage of [sessions](session) in which a us…