Interaction to Next Paint (INP): The metric that will replace First Input Delay in Core Web Vital reports from March 2024. Google introduced a new metric for page experience called Interaction to Next Paint (INP). INP is an experimental field metric that measures responsiveness. Responsiveness is how fast a page responds to user inputs and is thus a critical metric for tracking user experience scores.

Google puts a lot of emphasis on improving user experience.

Interaction to Next Paint (INP) is a field metric that measures page responsiveness. A page is considered responsive if it responds to user input quickly.

INP is particularly useful for measuring the responsiveness of a web page as it does not require any JavaScript or CSS code, unlike some other metrics. Instead, it measures only how fast the browser displays elements on the screen after receiving user actions.

Why is Interaction to Next Paint (INP) a field metric?

‍A field metric is a measurable factor or characteristic used to assess a specific field’s performance. A field metric requires user input to measure which is collected from real users.‍

Interaction to next paint is a field metric because it measures how quickly a user can interact with the next element on the page after the current element. This metric is important because it can help to gauge how smoothly the website is running and how quickly users can navigate through the pages.‍

Advantages of Interaction to Next Paint (INP)‍

1. It helps measure how fast a page responds to user inputs without any JavaScript or CSS code, as some other metrics do. It can be used for both mobile and desktop sites which makes it more universal than FID (First Input Delay).‍

2. It works across devices and browsers, which means that even if your website looks good on Chrome but not on Firefox, you can still measure its responsiveness using INP, as this metric does not depend on JavaScript or CSS code executed by browsers but just measures how fast your browser responds to user inputs without any external factors like network latency and rendering.‍

3. It can be used to measure the responsiveness of your homepage and any page on your website, especially pages that could have a lot of interactivity.‍

Drawbacks of Interaction to Next Paint (INP)‍

1. It is not supported by any third-party service right now. So if you want to use it, you will have to implement it yourself.‍

2. It depends on the Google Chrome browser, so if you want to get this data for your website, you will have to use Google Chrome as your primary browser (if you don’t already).‍

3. Even though it measures how fast a page responds to user inputs without any external factors like network latency and rendering, there still might be some internal factors that cause delays in the responsiveness of a page that INP does not measure. For example, suppose a webpage has JavaScript code that loads many resources from other domains (like ads or widgets). In that case, this could cause delays in that web page’s responsiveness even though it responds quickly to user inputs without any external factors like network latency and rendering.