LCP (Largest Contentful Paint)
Largest Contentful Paint measures how long the biggest visible element takes to render, usually a hero image, a video poster or a large text block. A good score is 2.5 seconds or less, timed from when the page first starts loading.
Why it matters for your rankings
LCP is the Core Web Vital that most closely matches what a visitor means by 'the page loaded'. It ignores background work and measures when the main content actually appeared on screen.
It is also the one most often failed and most fixable. The usual culprits are an uncompressed hero image, a render-blocking stylesheet, slow server response, or lazy-loading applied to the very element being measured. Each has a standard remedy. Because it is scored from real Chrome users over a 28-day window, improvements appear gradually rather than immediately, which leads teams to assume a fix did not work and revert it prematurely.
How to check it on your site
Identify the LCP element
PageSpeed Insights names the exact element being measured. Fix that element rather than optimising the page generally.
Compress and modernise it
If it is an image, serve WebP or AVIF at the displayed size and preload it with fetchpriority high.
Never lazy-load it
Lazy-loading the LCP element guarantees a poor score. Restrict lazy-loading to content below the fold.
Check server response time
Time to First Byte above 600ms caps your LCP no matter what you do to the front end.