INP will replace FID as a part of Core Web Vitals in March 2024
As an answer to FID’s limitations, Interaction with Next Paint (INP) emerges as an inclusive replacement metric. INP goes beyond simply measuring the delay of the initial input event but encompasses everything related to interaction: time delay between events and impact analysis of each input event on subsequent ones.
- Input Delay: The time between user interaction and the browser initiating event processing, akin to FID.
- Processing Delay: The time the browser takes to process event handlers efficiently.
- Presentational Delay: The time required for the browser to recalculate the layout and visually paint updates to the screen.
Why Google Launched INP
INP doesn’t limit itself to the first user interaction; instead, it aggregates all user interactions throughout a page’s lifespan, providing a Comprehensive metric that encapsulates the worst-measured score. By considering the entirety of a user’s interactions, INP offers a more nuanced understanding of a webpage’s responsiveness.Optimizing for INP
Unlike FID, which focuses on optimizing event queuing times and central thread availability, INP demands a more Comprehensive approach. It necessitates addressing the entire lifecycle of user interaction, including processing event handlers, recalculating layouts, and painting updates to the screen.Strategies for INP Optimization
Processing Delay Optimization
- Code Profiling: Rigorous code profiling is essential to identify and rectify performance bottlenecks. Understanding the intricacies of your codebase allows for targeted optimizations, ensuring efficient execution of event handlers.
- Debounce and Throttle Techniques: Employing debounce or throttle mechanisms for frequently firing event handlers prevents unnecessary processing and contributes to a smoother user experience.
- Code Splitting and Tree Shaking: Load only the necessary JavaScript components, employing code splitting and tree shaking to eliminate redundant code. That reduces processing delay and promotes a more streamlined loading process.
- Task Chunking: Break down lengthy JavaScript tasks into smaller, manageable chunks. This practice prevents prolonged occupation of the main thread, minimizing processing delays during user interactions.
Presentational Delay Optimization
- Optimizing Animations: Utilize the will-change property strategically to inform the browser about animated properties and elements. This proactive approach allows the browser to optimize the rendering of these elements, reducing presentational delays.
- Preferred Animation Properties: Opt for transform and opacity changes in animations, as these are less likely to trigger layout recalculations. That ensures smoother transitions without compromising on visual consistency.
- Content Rendering Optimization: Leverage properties like content visibility to render and update content only when necessary. Minimizing unnecessary rendering can mitigate presentational delays associated with content updates.
- Avoiding Forced Synchronous Layouts: Steer clear of immediately reading layout properties after writing them, as this can trigger forced synchronous layouts. Such layouts can significantly impact presentational delays, and avoiding them contributes to a more responsive UI.
Efficient Event Handling
- Deferring Non-Critical Events: Postpone the processing of non-critical events until the main thread is less occupied. Prioritize essential interactions to maintain a responsive user interface.
- Passive Event Listeners: Utilize passive event listeners for events like scroll and touch. That informs the browser that the event listener will not prevent a scroll or touch event, allowing for smoother interactions without waiting for the listener.
- Event Delegation: Instead of attaching event listeners to individual elements, attach them to a common parent. Using event properties, determine which child element was interacted with. That reduces the number of active event listeners and potential performance slowdowns.
Measuring and Monitoring INP
Tools for INP Measurement
- Vercel Speed Insights: Vercel Speed Insights is a valuable tool for measuring and gaining insights into your website’s Interaction with Next Paint (INP). It provides actionable data to guide optimization efforts.
- PageSpeed Insights: Google’s PageSpeed Insights offers a comprehensive analysis of your website’s performance, including insights into INP metrics. Leverage its recommendations to enhance user interaction responsiveness.
- Lighthouse’s Timespan Feature: with its Timespan feature, Lighthouse allows for a detailed examination of INP metrics over time. This historical perspective aids in identifying trends and making informed optimization decisions.
Real User Monitoring (RUM) for INP
- Real User Monitoring tools are crucial in continuously collecting user performance data. Despite INP’s evolving status, RUM tools offer real-world insights into how users interact with your website, facilitating ongoing optimization efforts.
Efficient Event Handling
- Deferring Non-Critical Events: Postpone non-essential events until the main thread is less occupied.
- Passive Event Listeners: Utilize passive event listeners for events like scroll and touch to maintain smooth scrolling without waiting for listeners.
- Event Delegation: Attach event listeners to a common parent, reducing the number of active listeners and potential slowdowns.