Why isn't INP the same in the CrUX report and in RUM data?

You may see different INP numbers on CrUX than in your RUM data. Here are a couple reasons this may occur: 

· CrUX reports data only from opted-in users in Chromium-based browsers, RUM through BT will collect INP in Chromium-based browsers for all users. 

· CrUX splits data between mobile and desktop browsers in all cases, with the default reporting in mobile.

· RUM uses JS-based collection, which relies on scoping on a webpage. JS tags loaded on the page are not scoped to view inside iframes, while the Chromium engine can collect interactions within iframes without issue. If iframes are present on a page, they may need to be monitored as a separate “page”.

· On SPA, BT reports an INP value per VT. As a result of the API we use to collect these values, we cannot report back the same INP for an SPA “full page” load as CrUX does, which reports on the longest INP across all VTs within an SPA “full page” load.