Add "scroll to end of page" option to Lighthouse

[tunetheweb]

Feature request summary

We get a lot of feedback where Lighthouse does not match CrUX for CLS (example). Often this is due to items "below the fold" without explicit dimensions. It would be good to be able to have a "Scroll to bottom of page after load" option in Lighthouse to pick those up - perhaps highlighted if lab CLS has large mismatch with field CLS?

What is the motivation or use case for changing this?

Help developers identify more CLS items using Lighthouse

How is this beneficial to Lighthouse?

This potentially allows more information to be gathered in Lighthouse for CLS, but also other audits. For example we can see the true size of the page once all lazy loaded components have been loaded.

It could also form the basis of more "conditional" audits, for example interaction audits using User flows to help identify INP issues.

[brendankenny]

Scrolling to trigger lazy-loaded content has definitely been a topic of conversation a number of times in the past. There are some tricky cases (e.g. more bespoke scrolling "experiences", infinite-scroll pages) but I especially like the idea of highlighting when there's a lab/field discrepancy.

This is also one of those actions that straddles the line between what can be done in a fully-automated Lighthouse navigation run and an arbitrary user flow, so two recent topics that come to mind:

• @connorjclark has been looking at some types of INP that could be automatically tested (e.g. interacting with hero elements), and this could fall into a similar place
• @adamraine has been thinking about audits that can be automated but can also interfere when part of a user flow (like full-page screenshots which require a page resize, new audit: bfcache eligibility  #13960 which requires a navigation, etc) and how to categorize them and allow them to be disabled, etc

[connorjclark]

@connorjclark has been looking at some types of INP that could be automatically tested (e.g. interacting with hero elements), and this could fall into a similar place

I need to finish evaluating this–and since this could potentially solve the problem here, let's wait on that (post-10.0) before deciding to add a specific option to scroll during tracing (at least for non-user-flow runs)

[moulinette]

Hi,
Coming with the same need: be able to generate a lighthouse report after a scroll to the end of page.
Have you something in progress around this ?