GLOSSARY
Largest Contentful Paint
Largest Contentful Paint, LCP, measures how long it takes for the largest visible element on a page, usually a hero image or a headline block, to finish rendering after a visitor requests the page. Google's target is under 2.5 seconds; the standard here is under 1.2 seconds.
Why it matters
LCP is the metric that most closely matches a visitor's actual perception of 'is this page loading.' A page that starts rendering instantly but takes five seconds for the main hero image to appear still feels slow to a real person, even if other technical metrics look fine. It also disproportionately affects mobile visitors on slower connections, exactly the audience most likely to abandon rather than wait, which makes LCP an equity issue as much as a technical one. It also interacts with render-blocking resources: a large script or stylesheet loading before the main content is allowed to paint can delay LCP even when the image itself is already well optimised.
What goes wrong when it's handled badly
The most common cause of a bad LCP score is an unoptimised hero image, uncompressed, wrongly sized for the display, or loaded after render-blocking scripts finish first. A hero image served at native camera resolution instead of the size actually displayed is a routine, avoidable cause of a multi-second LCP delay. A concrete example is a hero image loaded from a third-party CDN that itself responds slowly on a bad day, meaning the page's LCP depends on infrastructure entirely outside the site's own control unless that dependency is deliberately removed. Preloading the specific hero image as a priority resource, rather than letting the browser discover it only after parsing the rest of the page, is a common, effective fix once the cause is correctly diagnosed. Measuring LCP specifically on the pages that actually receive the most traffic, rather than only the homepage, is what surfaces where the real problem lives.