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Opened 8 months ago

Last modified 6 months ago

#59120 new defect (bug)

Measure interactivity metrics in performance tests

Reported by: swissspidy's profile swissspidy Owned by:
Milestone: Future Release Priority: normal
Severity: normal Version:
Component: Build/Test Tools Keywords:
Focuses: performance Cc:


This is a follow-up to #58360.

While we have some good load time metrics so far, we don't measure interactivity metrics yet.

We're particularly looking at these 3 metrics:

They can be measured using libraries like Lighthouse or

Interactivity metrics require some sort of interaction during the test, so we need to figure out specifics.

Change History (1)

#1 @swissspidy
6 months ago

Note that TBT is a lab metric that is not covered by web-vitals.js

In JS it could be done with something like

var totalBlockingTime = 0;
var observer = new PerformanceObserver(function (list) {
  let perfEntries = list.getEntries();
  for (const perfEntry of perfEntries) {
    totalBlockingTime += perfEntry.duration - 50;
  console.log({ totalBlockingTime });
observer.observe({ type: "longtask", buffered: true });


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