LCP measures perceived loading speed. The "largest element" is usually a hero image, a video poster, or a block of prominent text.
How to improve it
- Serve the hero image at the correct size with modern formats (AVIF, WebP).
- Preload the LCP resource in the head.
- Move third-party scripts off the critical path.
- Use a CDN close to your users.
Example
A news homepage drops LCP from 4.1s to 2.0s after preloading the hero image and deferring analytics tags.
How SEM Optimiser reports it
LCP is reported per URL with a breakdown of contributing factors — server response time, resource load delay, and render delay — so the largest lever is obvious.
Related terms
- Core Web Vitals
Core Web Vitals is a set of three page-experience metrics Google uses to measure loading performance, interactivity, and visual stability: LCP, INP, and CLS.
- INP (Interaction to Next Paint)
Interaction to Next Paint measures how quickly a page responds to a user's interactions across the whole session, and should be under 200 milliseconds.
- CLS (Cumulative Layout Shift)
Cumulative Layout Shift measures how much the visible layout of a page moves unexpectedly during load, and should be under 0.1.