What is Largest Contentful Paint?

Largest Contentful Paint marks the moment the biggest visible element, usually a hero image, a heading or a block of text, has rendered. It is the closest single number to 'the page has loaded' as a person perceives it. Google wants it at or under 2.5 seconds for 75% of visits. Anything after that and visitors start to doubt the page is working, especially on mobile networks.

LCP breaks down into four parts: time to first byte, resource load delay (how late the browser discovers the image), resource load time (how big it is) and render delay. Most slow LCPs come from a hero image that is discovered late because it is lazy-loaded or injected by JavaScript, is too large, or waits behind render-blocking CSS and fonts. A slow server adds its delay to everything.