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Home ยป [beta] Core Web Vitals: Interaction to Next Paint (INP)

[beta] Core Web Vitals: Interaction to Next Paint (INP)

You must have seen There is a new core web vitals (CWV) metric called INP introduced in the Page Speed Insights report. However, this is in beta stage, meaning experimental metric.

At a first glance, it seems like unnecessary metric to use as we already have hard time fixing other metric issues like CLS, LCP, FCP, TTBT, FID. However, the Google’s tool was calculating all of things until page load event happens. There was no accounting for interactions of the real world users.

Apparently the interactions that happen are around 90% after page load event, which Google PageSpeed Insights was not able to calculate. So there was a loop hole to trick Google pagespeed scores and get good ranking. This is mainly because Google checks the browsers main thread status and script and styles evaluation time.

The interaction time should be very less as per Google’s new INP metric. This means that after the page load, if user tries to tap, or click it should respond to it quickly. Interaction to next pain means after user interacts with the page, how soon it shows or reflects the interaction. If the UI changes then it means, browser re-painted the page and the latency that it has for re-painting should be less than 200ms seconds.

The following video shows how soon we show the first interaction repaint.

Also here is the infographic to understand how much time it should take and what is being considered as poor or bad INP.

Here is the elaboration of the same:

  • An INP below or at 200 milliseconds means that your page has good responsiveness.
  • An INP above 200 milliseconds and below or at 500 milliseconds means that your page’s responsiveness needs improvement.
  • An INP above 500 milliseconds means that your page has poor responsiveness.

There is a question about how it can track all interactions and how it will measure it consistently, how is it different from FID, what will be the INP value for sites which don’t have much interactions, etc. Some of which are answered in this article by Google’s Web Dev Site – https://web.dev/inp/

Do you have any specific questions on this new metric? please let us know in the comments below.

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