By Shad Super in Questions —

How Can I Measure Interaction to Next Paint (INP) Effectively Using Web Performance Tools, and What Benchmarks Should I Aim For?

Summary

The Interaction to Next Paint (INP) metric quantifies the responsiveness of user interactions on a webpage. Measuring INP effectively requires utilizing web performance tools like Lighthouse, Chrome User Experience Report (CrUX), and third-party services. This guide provides detailed steps to measure INP and outlines the benchmarks to aim for.

Understanding Interaction to Next Paint (INP)

INP is a Web Vitals metric indicating the latency between user interactions (such as clicks, taps, and keyboard inputs) and the next frame being painted. It's crucial for assessing perceived responsiveness and enhancing user experience.

Tools for Measuring INP

Lighthouse

Lighthouse is an open-source tool integrated into Chrome DevTools. To measure INP using Lighthouse:

  1. Open Chrome DevTools (F12 or right-click and select "Inspect").
  2. Navigate to the "Lighthouse" tab.
  3. Select the checkboxes for performance metrics, including INP.
  4. Click "Generate report" to analyze the web page.

Chrome User Experience Report (CrUX)

The Chrome User Experience Report (CrUX) collects real-user interaction data. Access INP metrics using the CrUX API or BigQuery to inspect responsiveness data at scale.

Third-Party Services

Several third-party monitoring tools provide INP metrics:

  • WebPageTest - Offers comprehensive performance testing and INP analysis.
  • SpeedCurve - Monitors front-end performance and captures INP metrics over time.

Benchmarks for INP

Good INP

An INP below 100 milliseconds is considered optimal, indicating a highly responsive user experience. Optimizing your website to consistently achieve this benchmark fosters smoother interactions.

Needs Improvement

An INP ranging from 100 to 250 milliseconds suggests usability issues. It's crucial to investigate and rectify elements causing interaction delays.

Poor INP

An INP above 250 milliseconds indicates significant responsiveness issues, degrading user experience. Immediate optimization strategies should be implemented to address these delays.

Tips for Improving INP

Optimize JavaScript Execution

Minimize the size and execution time of your JavaScript. Defer non-critical scripts or load them asynchronously to prevent blocking the main thread [Defer Non-Critical JavaScript, 2023].

Streamline Critical Rendering Path

Reduce the length of the Critical Rendering Path by minimizing render-blocking resources such as CSS and JavaScript. Prioritize loading essential components first.

Optimize Event Listeners

Ensure event listeners execute quickly. Avoid heavy computations during interaction events and use lightweight responses to user inputs [Making Interactions Fast, 2022].

Reduce Main Thread Work

Distribute computational tasks across Web Workers to offload heavy work from the main thread and enhance responsiveness [Multithreading in Web, 2021].

Conclusion

Effective measurement and optimization of INP require leveraging tools like Lighthouse and CrUX while adhering to best practices for efficient interactions. Achieving an INP below 100 milliseconds ensures a responsive and engaging user experience.

References