What does the "v3-1683361313937-9205711099327" mean in Web Vitals INP GA report?

My web page has a very poor field INP score, but I can't reproduce the poor INP via web vitals extension or devtools on my own. So the best attempt is to use web vitals JS SDK to collect real user data and send the data to GA.

However, when I checked the GA reports, it's all like this:

What is this? How can I locate the problem with all the v3-xxxxx labels?

This is a unique id for that event. It allows the event value to be overwritten if a later INP event comes in with a higher value. Other than that, knowing the actual value is not really useful to a user.

What is more useful, is logging the event_target available with the attribution build. This will show you the element clicked on (the button, or whatever) which should help you track down the slow event. See this post on how to log that.

I see you are using Universal Analytics, so you can use the Web Vitals Report to extract the target if you're already sending it to GA and display it a nice tool. Do be aware that UA is due to be switched off soon however and Web Vitals Report is not compatible with GA4.

Also be aware, that INP is a tricky metric to optimise for. Quite often a slow interaction can be due to the main thread just being busy with previous interactions. So the event you're looking at may not actually be that slow, and just be a victim of a generally overworked website.

We also recently updated the Web Vitals extension to log more data to help you identify slow interactions which may be another way to help find the issues on your website.