Google has recently updated its Core Web Vitals documentation, providing fresh insights into the Interaction to Next Paint (INP) metric, including why certain scoring thresholds were chosen. INP is now an essential component of Core Web Vitals, which are Google’s benchmarks for evaluating a site’s user experience, especially in terms of speed and interactivity.
What is Interaction to Next Paint (INP)?
Introduced as a Core Web Vital in spring 2024, INP measures how quickly a webpage responds to user actions like clicks, taps, and key presses. Unlike its predecessor, First Input Delay (FID)—which focused only on the delay of a page’s initial interaction—INP takes a more comprehensive approach by tracking the responsiveness of all interactions on a page. This metric aims to offer a clearer view of the user experience by reflecting how smoothly a site handles ongoing user inputs.
The official documentation explains:
“INP observes the latency of all interactions a user has made with the page, and reports a single value which all (or nearly all) interactions were beneath. A low INP means the page was consistently able to respond quickly to all—or the vast majority—of user interactions.”
Simply put, INP captures the time it takes for a webpage to visibly respond to user actions and provides a single score representing the consistency of that responsiveness.
Understanding INP Scoring
The recent documentation update clarifies the rationale behind the INP scoring thresholds, which categorize performance as either “good,” “needs improvement,” or “poor.” Here’s a breakdown of the thresholds:
– Good: Scores under 200 milliseconds (ms) indicate excellent responsiveness.
– Needs Improvement: Scores between 200 ms and 500 ms suggest the page could be more responsive.
– Poor: Scores over 500 ms are labeled as poor, indicating lag in response time.
Since achieving higher INP scores is typically easier on desktop devices due to faster processing power and more reliable network speeds, Google faced a challenge in setting realistic thresholds that account for mobile performance limitations. Rather than setting separate thresholds for desktop and mobile devices, Google opted for a universal standard based on mobile benchmarks. This unified scoring approach helps simplify expectations for website owners and reflects the reality that most internet traffic now comes from mobile devices.
Mobile-Optimized INP Thresholds
Google’s focus on achievable scores means that INP thresholds were specifically designed with lower-end mobile devices in mind. Given that a significant number of internet users access the web through budget smartphones, the team determined that a 200 ms threshold was realistic for most mobile devices, aligning with research that shows this timing offers a satisfactory user experience.
The documentation states:
“The more constrained nature of mobile devices means that most of the thresholds are therefore set based on mobile achievability. They more likely represent mobile thresholds—rather than a true joint threshold across all device types. However, given that mobile is often the majority of traffic for most sites, this is less of a concern.”
Benchmarking Against Popular Websites
To ensure INP thresholds were achievable in real-world scenarios, Google analyzed data from the top 10,000 websites. The analysis revealed that a majority of these popular sites fell short of the 200 ms “good” threshold, with many sites hitting 300 ms or more. To avoid setting an unachievable benchmark, Google established the 500 ms threshold for “poor” scores, accommodating the performance variability of even the most-visited sites.
The new documentation elaborates:
“When we look at the top 10,000 sites—which form the vast majority of internet browsing—we see a more complex picture emerge… On mobile, a 300 ms ‘poor’ threshold would classify the majority of popular sites as ‘poor’ stretching our achievability criteria, while 500 ms fits better in the range of 10-30% of sites.”
Thus, Google arrived at a 200 ms benchmark for “good” and 500 ms for “poor,” ensuring that top sites can meet these thresholds while still providing a satisfying experience for mobile users.
Moving Forward: A Clearer Understanding of INP
With these new insights, developers and site owners now have a clearer sense of how Chrome sets achievable targets for web performance, particularly for mobile users. As web technologies continue to evolve, Google’s approach to Core Web Vitals, including INP, highlights its commitment to optimizing the user experience for all types of devices—especially the mobile devices most users rely on.
New Insights in Core Web Vitals: Interaction to Next Paint (INP)
