Persist FID value between pages on HUD

[gilbertococchi]

FID issues due to 3rd parties on click events are quite hard to troubleshoot so far and I am wondering if the web-vitals-extension HUD Overlay can store the previous page FID value to help spotting this kind of issues.

Below an example on Montblanc IT https://www.montblanc.com/it-it site where FID becomes 165ms but it's impossible for the user to notice that on the next page and it correlates with a 3rd party script Function Call.

[addyosmani]

This is an interesting feature request. If I'm reading this correctly, there is interest in adding History support to the extension so that, perhaps on navigation to a new page/route, we temporarily persist the set of CWV values previously experienced and perhaps give you some drill-down:

Previous values

• https://foo.com/about - LCP: 2.4s, FID: 0.3s, CLS: 0.4
• https://foo.com/contact - LCP: 2.6s, FID: 0.4s, CLS:

Something like the above? If not could you clarify the request? I would also be interested in @rviscomi's thoughts here.

[gilbertococchi]

Exactly, having some way to browse/inspect previous values, especially FID would be beneficial considering the metric nature.

In the screenshot I've added you can tell that the Extension is on Page2 after having clicked on a button on Page1 but only thanks to the "Performance" session screenshots of the Page1 FID value being populated I was able to tell Page1 FID was of 165ms.

[rviscomi]

I filed https://github.com/GoogleChrome/web-vitals-extension/issues/77 for a different reason but I actually think it would solve this use case. Console logs can be persisted across navigations, so it should be straightforward to refer back to the previous page's FID.

I think the technical bar for console logs is really low, so that may be a lower friction way to achieve the same result without having to fit it into the UI somehow.

[gilbertococchi]

+1, great idea, I believe using some simple Console Logs would solve the gap here!