Largest Contentful Paint change in Chrome 112 to ignore low-entropy images

In Chrome 112, LCP will begin to ignore images with very low content relative to their display sizes.

LCP has historically ignored full screen background images, as well as solid or simple gradient backgrounds when implemented through CSS. That heuristic discounts paints which are not contentful, but just serve as backgrounds or placeholders for other content.

This change extends that heuristic to other images as well, when those images have very little content, when compared to the size at which they are displayed. The threshold is currently 0.05 bits of image data per displayed pixel, and images which fall below this threshold will not be considered for LCP. We expect that this threshold will mostly cover large simple background images or viewport overlays, as well as simple placeholders which are sometimes used for lazily- loaded images.

How does this affect a site's metrics?

By ignoring ver low-content images, Chrome will instead report the first paint with either text or a more contentful image as LCP. This may result in LCP times increasing, if a low-content background was being painted very early, or if a low-content placeholder was being used to reserve space for a more contentful image which loaded later. This may also improve LCP in cases where a low-content background or viewport overlay was being added to the page after other content.

When were users affected?

This change was launched to Chrome users starting on roughly April 6, 2023, and was rolled out to existing Chrome installs. This roughly coincides with Chrome 112, although previous versions (back to Chrome 109) will also pick up this change.