Largest Contentful Paint Bug Fixes in M88

Bug Fixes in Chrome 88

In Chrome 88, some bug fixes were made in the chromium implementation.

The bug fixes are:

Full viewport images, which are visually equivalent to background images, are no longer considered as the largest contentful paint. Source code for this change.
Largest Contentful Paint stops recording after an input in an out of process iframe. This change only affects Chrome's reporting of Largest Contentful Paint in the Chrome User Experience Report, as the API doesn't report iframe content to the main frame. Source code for this change.
Prior to Chrome 88, Largest Contentful Paint had a bug where it incorrectly classified some images as invisible. This could happen in the case of offscreen or tiny placeholder images which were replaced with large visible images. The bug has been fixed, and the large visible images are now counted as possible largest contentful paints. Source code for this change.

How does this affect a site's metrics?

Each change only affects sites with specific types of content.

The change to ignore full viewport images as potential largest contentful paints will improve Largest Contentful Paint times for pages with background images. This is intended as Largest Contentful Paint attempts to time when the main content on the page is visible, and this generally is not background images.

The change to stop recording after an input in an out of process iframe will improve Largest Contentful Paint times on sites which have cross-process iframes.

The bug fix for invisible elements may result in increased Largest Contentful Paint timings for sites using a placeholder pattern that swaps in the largest contentful image.

When were users affected?

Chrome 88 is currently scheduled to be released the week of January 19, 2021.