Largest Contentful Paint (LCP)
LCP measures when the largest visible element finishes rendering. Under 2.5s is good — here's how the fix usually comes down to one element.
What it is
Largest Contentful Paint (LCP) measures the time from navigation start until the largest image or text block in the viewport has rendered — a stand-in for 'when does this page feel loaded' rather than 'when did the first byte arrive'. It's one of Google's three Core Web Vitals.
This scanner grades it, not pass/fail: under 2.5 seconds is good and reports nothing, 2.5-4s costs a medium-severity finding, and anything slower costs a high-severity one — the same thresholds Lighthouse and Chrome's own field data use.
Why it matters
LCP is a ranking signal in Google Search, and — more directly — a proxy for how long a visitor stares at a blank or half-loaded page before there's anything to read. A slow LCP is disproportionately caused by one element: an unoptimized hero image, a webfont blocking text render, or a render-blocking script ahead of the content.
Fixing it is usually about that one element specifically — preload it, serve it from a fast path, remove whatever's rendering ahead of it — rather than a general performance audit of the whole page.
How to fix it
with a reference doc<link rel="preload" as="image" href="/hero.jpg" fetchpriority="high">Related checks
3This is one of the 75 checks the scanner runs. See what we check for the full list, every severity weight, and how the score is computed from them.