Interaction to Next Paint (INP) is a web performance metric that measures user interface responsiveness – how quickly a website responds to user interactions like clicks or key presses. It’s a replacement for First Input Delay (FID) metric as the new Core Web Vital metric for responsiveness effective March 2024.
How does it compare to FID?
First Input Delay (FID) only reports the responsiveness of the FIRST TIME a user interacts with the page. Even though first impressions matter, the first time you do something on a webpage doesn’t always show what all your experiences will be like. FID, or First Input Delay, only looks at the delay that happens when you try to do something for the first time on a webpage. It’s about the time your browser has to wait before it can start dealing with what you’re trying to do, often because it’s busy with other tasks.
INP solves FID’s limitations and provides us with a more detailed measure of user-perceived responsiveness.
Unlike FID, which focuses on the first interaction, Interaction to Next Paint (INP) considers all interactions on a webpage. Instead of just measuring the delay, INP captures the entire process—from the start of your interaction, through the event handler (the part of the webpage that responds to your action), and until the browser finishes painting the next frame. In simpler terms, INP provides a more thorough measure of how responsive a webpage feels to you, taking into account the full time it takes for your actions to be processed and for the page to update visually.
For example, if you load a page and only click a button once, FID notes the time it takes for your click to register. INP, on the other hand, not only records that time but also looks at what happens next—how long it takes for the webpage to process and show the result. If this is your only action on the page, INP considers this whole process and reports it as the longest duration you experienced. So, with just one interaction, INP gives a fuller picture of how interactive the webpage is because it includes the time it takes to process and show the result.
INP is classed as ‘Good’ if the final reported value is less than 200 ms. INP is classed as ‘Needs Improvement’ between 200ms and 500ms. Any measurement above 500 ms is classed as ‘Poor’.
What do I need to do to prepare for switch to INP?
INP will start affecting Google Search rankings when it becomes a Core Web Vital in March 2024. To get ready, websites need to improve interactivity beyond the initial load of the site.
In order to improve INP, you need to collect some data about it first. Since INP is best reported from field data, the data must come from real users interacting with web pages on real browsers.
The first step to understanding INP on a website is to enable a Real User Monitoring (RUM) provider. RUM providers collect performance data from real browsers, and process the data so that it can be aggregated and analyzed. A RUM provider will give you not only a page’s INP value, but also contextual data that highlights what specific interaction was responsible for the INP value itself, whether the interaction occurred during or after page load, the type of interaction (click, keypress, or tap), and other valuable information.
Improving INP involves enhancing three specific time periods: the delay when you input something, the time it takes for the webpage to process your input, and the time it takes to display the result. So, making INP better means working on these three parts individually.
That’s why it’s a good idea to begin early and gather as much information as you can before the change happens.
