| |
| # Cumulative Layout Shift Changes in Chrome 98 |
| |
| ### Record CLS value at the first OnHidden in addition to tab close in UKM |
| |
| The Cumulative Layout Shift score will be recorded the first time a page moves |
| from the foreground to the background, which can fill in for the layout shift |
| values that are not able to be recorded at tab close, the current CLS reporting |
| point. |
| [Source code for this change](https://chromium-review.googlesource.com/c/chromium/src/+/3251379). |
| |
| ## How does this affect a site's metrics? |
| |
| There should be an increase of reporting the Cumulative Layout Shift value on |
| desktop sites which have FCP values. |
| |
| Note this only affects UKM (and so CrUX) reporting of CLS and does not affect |
| PerformanceObserver observations as measured in JavaScript. |
| |
| ## When were users affected? |
| |
| The updated metric was added in Chrome 98 which we released in the week of |
| February 1, 2022. The CrUX report included this update starting with CrUX |
| BigQuery 202207 (August 9, 2022). |
