[danielvaughn]

Based on the fact that they're hooking into events like onclick, I'd say that they are not looking at traditional form submits, because then the metric would just effectively be First Contentful Paint or something. My interpretation is that they are indeed looking at first paint after an event handler has been fired on the same page.

[iamakulov]

This is correct (source: working in web perf for 5 years).

INP is the time between you click/press a key/etc and the moment the next paint happens. It’s only measured for on-page interactions, not for navigations.

It’s basically like http://danluu.com/input-lag/ but as a web metric.

[danielvaughn]

Thanks for confirming, yeah that makes sense. Side note, that input-lag thing is a very cool resource.