wehub-resource-sync
1.3 KiB
1.3 KiB
Elements and Size for LCP
What Elements are Considered?
The types of elements considered for Largest Contentful Paint (LCP) are:
<img>elements: The first frame presentation time is used for animated content like GIFs.<image>elements inside an<svg>element.<video>elements: The poster image load time or first frame presentation time, whichever is earlier.- Background images: Elements with a background image loaded using
url(). - Block-level elements: Containing text nodes or other inline-level text element children.
Heuristics to Exclude Non-Contentful Elements
Chromium-based browsers use heuristics to exclude:
- Elements with opacity of 0.
- Elements that cover the full viewport (likely background).
- Placeholder images or low-entropy images.
How is an Element's Size Determined?
- Visible Area: Typically the size visible within the viewport. Extending outside, clipped, or overflow portions don't count.
- Image Elements: Either the visible size or the intrinsic size, whichever is smaller.
- Text Elements: The smallest rectangle containing all text nodes.
- Exclusions: Margin, padding, and borders are not considered toward the size.
- Containment: Every text node belongs to its closest block-level ancestor element.