Favour Nwachukwu
May 31st, 2023

INP to replace FID

First Input Delay : FID measures how long it takes for the browser to process user interaction, limited to clicks, key-down, mousedown and pointerdown. In simpler terms, FID measures responsiveness, but over time there’s been a couple of limitations. FID only measured the delay, the time it takes before an interactive element becomes responsive.

Limitations of FID
  • It only measures the first interaction after a page loads. If a user interacts with a page multiple times, FID will only measure the first interaction.
  • It is not always representative of the overall responsiveness of a page. A page can have a low FID but still be slow to respond to other interactions.
  • FID is often an easy measure to achieve, and as a result, it has been easing people into a false feeling of comfort.

Chrome in a bid to resolve these limitations, an experimental metric was introduced in 2022 named Interaction to Next Input (INP).

What Is INP?

INP is a metric that measures how responsive a page is to all user actions. It does this by looking at the latency of all clicks, taps, and keyboard actions that happen during a user's visit to a page. Leaving outliers, the final INP number is the longest interaction that was seen.

After a year of testing and gathering feedback, Google has announced INP will be replacing FID, effective from March 2024.

What This Means

Google is concerned with ensuring that every user has the greatest possible web experience. Furthermore, because Chrome's objective is to assist developers in focusing on crucial metrics for a better user experience. Here is our interpretation of INP replacing FID:

For Google Search Console: In March 2024, the new metric INP, will replace FID as part of the Core Web Vitals. Later this year, the CWV report will incorporate INP, helping site owners and developers assess their websites based on the new metric. Once INP replaces FID, the report will no longer include FID measurements, prominently displaying INP as the new responsiveness metric.

Since Google's introduction of Core Web Vitals, site owners have been recommended to achieve good Core Web Vitals in order to achieve success in Search and deliver a great user experience in general.

So, if you've been following the CWV recommendations, you're already concerned about the responsiveness of your website. Improving FID is a good basis for INP; the good news is that INP provides a clearer picture of your site's responsiveness because it is a more accurate metric. This will improve the overall user experience of your site.


Chrome usage data shows that 90% of a page's time is spent after it loads, therefore responsiveness measurement throughout the page lifecycle is crucial. INP measures this.

A fast-response page is responsive. When a page responds to an interaction, the browser displays visual feedback in the next frame.

Some interactions will take longer than others, but it's crucial, especially for more complex interactions, to give the user a sense of progress as soon as possible. The earliest window of opportunity to do this is the time before the next painting.

Therefore, the goal of INP is to track the amount of time that the next paint is being blocked, as opposed to all of the future repercussions of the interaction, such as network requests and UI updates from other asynchronous activities. Users may get the idea that the page isn't responding to their input if they don't see any changes immediately.

The primary objective of INP is to minimize the amount of time it takes to render the next frame once a user initiates an interaction.

How To Measure INP

INP can be measured in the field as well as in the lab (with some effort) using a number of techniques. The easiest way to quantify your website's INP is to collect metrics from real-world users in the field.

Field tools
Lab tools
What Is Considered Good INP

To make sure you're giving users good flexible experiences, the 75th percentile of page loads recorded in the field, broken down by mobile and desktop devices, is a good measure:

  • 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.

INP is calculated after the user exits the page, yielding a single value that represents the page's overall responsiveness over the course of the page's lifecycle. A low INP indicates that a page is consistently responsive to user input.

How To Improve INP
  • Reduce the number of JavaScript files on your page.
  • Optimize your images and videos.
  • Use a CDN to serve your static content.
  • Minify and gzip your HTML, CSS, and JavaScript files.
  • Avoid using heavy plugins and extensions.
  • Test your website on a variety of devices and browsers.

To know more about optimising your websites for INP, web.dev has many resources on this, see here.

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