INP Metric Officially Replaces FID in Core Web Vitals Assessment

Google has completed the transition from First Input Delay (FID) to Interaction to Next Paint (INP) as the official responsiveness metric in Core Web Vitals. The transition which was announced in May 2023 and completed in March 2024 represents a significant change in how Google evaluates page responsiveness.

Why INP Replaces FID

FID measured only the delay before the first user interaction was processed, ignoring the time to actually complete the interaction and update the screen. INP measures the full duration from user interaction to visual response providing a much more comprehensive view of page responsiveness. FID was also frequently near zero for most sites making it a poor differentiator. INP captures the full interaction lifecycle including event processing time and rendering time.

Impact on SEO Rankings

Sites that were passing Core Web Vitals under FID but have poor INP scores may now be failing the responsiveness metric. Early data suggests that approximately 15 to 20 percent of sites that were passing FID are now failing INP. This creates a new optimization opportunity for sites that improve INP ahead of competitors. Sites already passing INP have gained a relative advantage over competitors who were relying on their FID passing status.

INP Optimization Priority

Google recommends focusing optimization efforts on: reducing main thread blocking time by breaking long tasks into smaller chunks, optimizing event handlers to minimize processing time, reducing third-party script impact through facades and lazy loading, and using Web Workers for heavy computation that does not need to run on the main thread.

Tools for INP Measurement

PageSpeed Insights now shows INP scores alongside other Core Web Vitals. Chrome DevTools Performance panel provides detailed interaction analysis. The web-vitals JavaScript library supports INP measurement for custom RUM implementations. Google Search Console Core Web Vitals report shows INP performance across your site.

Recommended Next Steps

Audit your site for INP performance immediately. Identify pages with poor INP scores. Implement the recommended optimization techniques. Monitor improvement using field data from CrUX and Search Console. Consider INP in your development review process for new features.