What Is Interaction to Next Paint (INP)? How to Improve INP

Brock Munro
December 7, 2023
May 16, 2024
What Is Interaction to Next Paint (INP)? How to Improve INP

Interaction to Next Paint (INP) is a new core web vitals (CWVs) metric that focuses on measuring a webpage’s responsiveness from the moment a user interacts with it to the point where the visual response is rendered.

This metric is pivotal to understanding and enhancing a website’s user experience (UX), as it directly relates to how quickly a page can respond to user inputs.

Google introduced INP as a replacement for First Input Delay (FID) in the CWVs as part of its ongoing efforts to enhance web performance and UX. The announcement highlights the importance of INP in measuring the responsiveness of web applications and sites, marking a step towards a more user-centric web.

In this article, we’ll go into the intricacies of INP, exploring its significance and the methods to optimize it for a smoother web experience. Whether you're a web developer, a site owner, or simply interested in web performance, the knowledge and tools you find here should help you use the INP metric effectively.

What Is Interaction to Next Paint? 

Interaction to Next Paint (INP) is the latest addition to Google’s core web vitals metrics and measures a website or web application’s responsiveness to user interactions.

It specifically quantifies the time elapsed between a user-initiated action (such as a click, tap, or key press) and the moment the page visually updates in response to that action. This metric is crucial in evaluating how quickly and effectively a website can respond to user input.

A key aspect of INP is that it measures responsiveness throughout the entire lifecycle of a user's visit to a page, not just the initial interaction. This makes it a more comprehensive metric than its predecessor, First Input Delay (FID), which only accounts for the delay in processing the first input.

INP is particularly relevant for pages that are interacted with over a longer period, such as single-page applications, where it provides a more accurate representation of the overall user experience (UX).

What Is Interaction to Next Paint

How Is Interaction to Next Paint (INP) Measured?

Understanding how Interaction to Next Paint (INP) is measured involves breaking down the process into its core components. INP is not just about the initial response to an interaction but encompasses the entire sequence from the user's action to the visual update on the page.

Steps in Measuring INP

  • Capturing user interaction: The measurement begins the moment a user interacts with the page. This interaction could be a click, a tap on a touchscreen, or a keypress on the keyboard. INP focuses on these specific types of interactions, as they are direct and intentional actions requiring a response from the page.
  • Input delay: The next phase in the measurement is the input delay. This is the time taken before the page starts processing the interaction. During this phase, the browser might be busy with other tasks, which can delay processing of the user's input.
  • Processing time: Once the input is being processed, the next phase is the processing time. This involves running the event handlers associated with the interaction. These event handlers are typically JavaScript functions that execute in response to the user's action. The processing time can vary depending on the complexity of the tasks these handlers perform.
  • Presentation delay: The next phase is the presentation delay after processing the input. This is the time taken for the page to render the visual response to the interaction. It includes tasks like recalculating the layout of the page, executing any CSS changes, and repainting the page content to reflect the interaction.
  • Visual update: The final step is the visual update on the page, which is the culmination of the interaction process. This is when the user sees the result of their action, such as a menu opening, a form submission indication, or any other visual change on the page.
  • Calculating INP: The total INP is calculated by adding the input delay, processing time, and presentation delay. This gives a comprehensive measure of the time from the user's initial interaction to the next paint, which reflects the visual update on the page.

What Is a Good INP Score? 

To ensure a satisfactory user experience (UX), websites should aim for an INP of 200 milliseconds or less. This benchmark is considered a good threshold for most users, indicating that the website is responsive and interactions are processed quickly.

When evaluating INP scores, it's important to consider the variability of user experiences across different devices and conditions. Therefore, a practical approach is to measure the 75th percentile of page loads, taking into account both mobile and desktop devices. This method helps in capturing a more comprehensive view of the user experience, ensuring that the majority of users are receiving a responsive experience.

A high INP score can significantly affect the user experience, especially on websites with numerous interactive elements, such as text editors or games. In these cases, a high INP indicates a risk of poor user experience due to delayed responses to user interactions. Conversely, a low INP score suggests the website is consistently responsive, contributing to a smoother and more enjoyable user experience.

What Is a Good INP Score

Difference Between First Input Delay (FID) and Interaction to Next Paint (INP)

Understanding the difference between First Input Delay (FID) and Interaction to Next Paint (INP) is crucial for web developers and site owners aiming to optimize user experience (UX). While both metrics are designed to measure interactivity and responsiveness, they focus on different aspects of user interactions.

First Input Delay (FID)

First Input Delay measures the time from when a user first interacts with a page (like clicking a link or tapping on a button) to the time when the browser is actually able to begin processing event handlers in response to that interaction.

FID helps understand UX during the loading phase of a page. It's all about the initial impression: how quickly a page can start processing an interaction after a user first tries to interact with it.

For example, consider a user who clicks on a dropdown menu as soon as the page loads. FID would measure the time from the user's click to when the dropdown begins to appear. If the browser is busy loading the page, there might be a noticeable delay, leading to a poor UX.

Interaction to Next Paint (INP)

Interaction to Next Paint (INP), on the other hand, is a more comprehensive metric. It measures the latency of all user interactions during the lifespan of a page visit, not just the first one. INP captures the entire duration from when the user interacts with the page to when the visual response of that interaction is rendered on the screen. This includes the time taken for input delay, processing the interaction, and the presentation delay.

To illustrate, imagine a user interacting with various elements on a webpage, such as typing in a search field, selecting items from a menu, and clicking on links. INP would measure the responsiveness of each of these interactions, providing a broader view of the overall interactivity of the page throughout the user's visit.

How to Measure Interaction to Next Paint (INP)

INP can only be measured with field tools as it requires real user interaction data. These tools include:

  • PageSpeed Insights: Provides a user-friendly interface to view INP scores. PageSpeed Insights provides the 75th percentile score for the last 28 days.
PageSpeed Insights
  • Google BigQuery (CrUX Dashboard): Offers a more historical context of INP scores. Google measures all interactions real Chrome users have with a page and stores them in the CrUX dataset.
Google BigQuery (CrUX Dashboard)
Lighthouse Tool

Core Web Vitals Visualizer

While the CrUX dataset is the final source for INP metrics, it is highly anonymized and doesn't provide real-time monitoring or detailed filtering. Web performance consultants typically rely on real user monitoring (RUM) for more detailed insights.

How to Optimize Interaction to Next Paint? 

Optimizing Interaction to Next Paint (INP) is key to enhancing a website’s responsiveness and user experience (UX). Here are detailed tips on how to optimize INP:

1. Minimize CPU Processing on Your Page

  • Asynchronous code execution: Run more of your code asynchronously to ensure that the user gets an immediate UI update, even if some background processing is still ongoing.
  • Profile website code: Use tools such as the DevTools performance profiler to understand what's happening on the main thread and identify areas for optimization.
  • Review third-party scripts: Assess if third-party scripts are impacting your site's responsiveness and configure or defer them as necessary.

2. Reduce Input Delay

  • Break up main thread tasks: Reduce and break up background CPU activity on the main thread to minimize input delay.
  • Total Blocking Time (TBT) metric: Use this metric in lab data to identify background activities that could be blocking user interactions.
  • Optimize third-party code: If third-party scripts are causing delays, explore options to reduce their impact or load them only when necessary.

3. Optimize Processing Time

  • Efficient code execution: Investigate where the browser spends most of its time and optimize those parts of your application.
  • Avoid unnecessary renders: In frameworks such as React, ensure that components are not rendering unnecessarily.
  • Layout work reduction: If a significant amount of CPU activity is the result of layout work, find ways to reduce layouts and repaints.

4. Update UI Before Heavy Processing

  • Immediate feedback: Provide visual feedback (like a spinner) before starting CPU-intensive tasks.
  • Use web workers: For heavy JavaScript processing, consider using web workers to run tasks off the main thread.

5. Avoid Blocking Dialogs

  • Non-blocking UI elements: Replace native alert, confirm, and prompt dialogs, which block the main thread, with non-blocking UI elements.

6. Reduce Presentation Delay

  • Simplify page updates: If rendering page content is slow, focus on showing important content first to deliver the next frame more quickly.
  • Manage queued interactions: Be aware of how queued interactions can add to the presentation delay and manage them efficiently.

7. General Best Practices

  • Monitor performance regularly: Continuously monitor your site's performance using tools like Google PageSpeed Insights, Lighthouse, and real user monitoring (RUM) solutions.
  • Stay up to date with CWVs: Keep track of changes in core web vitals metrics and adjust your optimization strategies accordingly.

By implementing these strategies, you can significantly improve your website’s INP, leading to a more responsive and user-friendly experience. Remember, optimizing for INP is an ongoing process that requires regular monitoring and adjustments based on user interaction patterns and website updates.

Final Thoughts

Interaction to Next Paint (INP) is a key metric for assessing the responsiveness of web pages. It offers a comprehensive view of how quickly a site responds to user interactions, surpassing the scope of First Input Delay (FID) by measuring the latency of all interactions, not just the first.

We've discussed how to measure INP using tools such as PageSpeed Insights and Lighthouse and explored strategies for optimization, such as minimizing CPU processing and reducing input delay. These steps are crucial for enhancing user experience (UX) and website performance.

Optimizing site performance can also help publishers improve their ad revenue. A well-optimized site is more likely to encourage audiences to visit more than just once, after all. If you’re looking to improve your site’s monetization, then consider getting in touch with us to learn more about how we’ve helped more than 350 publishers across 60 countries increase their revenue since 2015.


What Does User Interaction Mean?

User interaction refers to any action a user takes on a webpage, such as clicking a button, tapping a link, or typing in a text field. These interactions are how users communicate with a website, initiating a response or change on the page. User interactions are fundamental to the functionality of web applications, as they trigger events that lead to dynamic changes, content updates, or navigation within the site.

Is INP a Core Web Vitals Metric?

INP will replace First Input Delay (FID) as a Core Web Vitals metric in March 2024. CWVs are a set of metrics that Google uses to evaluate the user experience (UX) of a webpage, focusing on aspects such as page load, interactivity, and visual stability.

What User Interactions Does INP Consider?

INP considers interactions such as mouse clicks, taps on a touchscreen, and key presses. These are direct actions that users take to interact with a website. INP does not include passive interactions like hovering or scrolling. The metric focuses on active engagements where the user expects a response from the website, making it a valuable measure of a site's interactive performance.

What Are Cookies?

Cookies are small data files stored on a user's device by a web browser when visiting websites. They are used to remember information about the user, such as login details, preferences, and browsing history.

Cookies help personalize the user experience, maintain session states, and track user behavior for analytics and advertising purposes. While essential for many web functionalities, cookies also raise privacy considerations, leading to regulations on their usage and user consent.

What Is an Example of Interaction to Next Paint?

An example of Interaction to Next Paint would be a user clicking a “Submit” button on a form and the time it takes for the confirmation message to appear on the screen. INP measures the duration from the click to the visual update of the confirmation. This metric helps with identifying slow interactions, which is essential if you want to improve your site’s user experience.

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