LCP Audit Tool

Chrome 146 aligns Largest Contentful Paint candidate emission with the W3C specification. This tool observes real LCP entries in your browser, lets you inject elements to trigger new candidates, and flags spec-alignment differences.

Live PerformanceObserver — largest-contentful-paint

#ElementSize (px²)Render msLoad msURL / contentStatus
No LCP candidates yet — scroll down to the stage or interact with the page.

Stage — Inject Elements

Add elements below to trigger new LCP candidates. The observer above will capture each emission.

Spec-Aligned vs Pre-v146 Candidate Rules

Pre-v146 Chrome
  • Emitted candidates for elements removed from the DOM after paint (spec says: stop tracking removed elements).
  • Could emit candidates for elements with zero visible area (e.g. opacity: 0).
  • Counted portions of images outside the viewport in the size calculation.
  • Video poster images were not always promoted to candidates consistently.
v146 — Spec Aligned
  • Elements removed from the DOM are no longer promoted as final LCP candidates.
  • Zero-visible-area elements (opacity:0, visibility:hidden) are excluded.
  • Image size is clipped to the intersection with the viewport for scoring.
  • Video poster images follow the same timing as equivalent <img> elements.

Common LCP Pitfalls

Click "Test" to inject each pattern and see whether it becomes an LCP candidate under the v146 spec.