Can you add new timing value for that? Its really important to know, when user see the first pixel of site (but not the white screen).

The issue with first paint is that it's both hard to define and of dubious value as a metric. For some pages a white screen is a legitimate paint, while many others don't care about first pixel and want to track when particular elements become visible. Really, what you're after is "first meaningful paint", but we can't define this in the spec, since this varies for every site. As such, this is a wontfix for Navigation Timing.

That said, note that Frame Timing will allow you to track when paints happen, so if you want you can track first paint. In the future, with some of the Houdini pieces in place, we may be able to offer an even better solution.

I dont understand, why it is in DevTools, but cannot be in Navigation Timing?

Why you cant just add another timestamp of moment when visibilityState changing from "hidden" to "visible"?
Name it visibilityStateChange, or something like that, if you dont like term "first paint".

There are many services that measure render time for your site, but you cannot measure it by JS in browser...

dubious value as a metric

I want to know how many time user waits from "enter" click till he is able to see any content on my site.

I dont understand, why it is in DevTools, but cannot be in Navigation Timing?

Just because it is in DevTools doesn't mean it's a good metric. Something like SpeedIndex would make a lot more sense, but that is subject to a lot of security concerns.

Why you cant just add another timestamp of moment when visibilityState changing from "hidden" to "visible"? Name it visibilityStateChange, or something like that, if you dont like term "first paint".

You can record it yourself already.

There are many services that measure render time for your site, but you cannot measure it by JS in browser...

I'm not saying that "rendering performance is not important". Rather, I'm pointing out that "first paint" is not sufficient, and we need a better solution. Some combination of Frame Timing, Visibility Observer, and Houdini will get us there, but it'll take some time.

Mkay. Thanks for answers.

Im disappointed because I make some "async css" improvements on our project right now, and I will not be able to prove strictly, that real users will be waiting much less time for the content...
I already have some beauty normal distributions of DOMContentLoaded times from over tens of thousands of users, but that "before" data goes nowhere, because I will not be able to collect another "after" data for comparison.

I hope the future is coming.

I agree with Ilya here. Frame timing should give you a finer grain metric regarding paint.