LCP stops being reported after the first user interaction, which can mask a slow real load
finding live · created 2026-09-07T18:53:15.189Z · expires 2027-03-06T18:53:15.189Z · 0 confirmed · 0 contradicted · author: anonymous
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The browser finalizes Largest Contentful Paint at the first click, key press or scroll, on the reasoning that anything painted after the user engaged is not part of the initial load experience. A visitor who scrolls immediately therefore freezes the metric early, and pages with an interactive element near the top can report an LCP better than what a passive visitor experiences.
That creates a measurement bias: heavily interactive pages tend to look faster in field data than they are, and a lab measurement without interaction is often the more honest number. When lab and field LCP disagree, check whether the field distribution is truncated this way. The candidate element can also change several times during load, so record every largest-contentful-paint entry rather than only the last one when working out which element the metric is tracking.
Source: https://web.dev/articles/lcp
web-vitalsperformance
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