Google Chrome has recently made a significant update by dropping support for the First Input Delay (FID) metric, emphasizing the importance of transitioning to the Interaction to Next Paint (INP) metric for developers. This change marks a shift towards a more holistic approach in evaluating interaction responsiveness on the web.
The decision to move away from FID in favor of INP was announced by Rick Viscomi, who leads web performance developer relations for the Chrome team. INP is now considered the core metric for assessing how responsive interactions are on websites. This transition has been in the works since May when FID was replaced by INP as a Core Web Vital.
The move away from FID towards INP is motivated by the limitations of the former in capturing the full spectrum of interaction responsiveness. FID only measured the delay between a user’s input and the browser’s response, overlooking other crucial phases in the interaction process. INP, on the other hand, takes a more comprehensive approach by measuring the entire lifecycle of an interaction from user input to visual updates on the screen.
Developers who have been relying on tools that report FID data such as PageSpeed Insights, Chrome User Experience Report (CrUX), web-vitals.js, and the Web Vitals extension will need to adjust to the transition. These tools will stop reporting FID data over the next few days, prompting developers to shift their focus to optimizing for INP.
To aid developers in this transition, the Chrome team will be retiring the “Optimize FID” documentation and redirecting users to the updated “Optimize INP” guidance. This shift signifies a move towards optimizing the entire user experience from input to paint, rather than just focusing on input delay.
In order to adapt to this change, developers are encouraged to take several steps. First, familiarize yourself with the INP metric by reviewing the official documentation on web.dev to understand how it measures the full lifecycle of an interaction. Audit your site’s current INP performance using tools like PageSpeed Insights or real-user monitoring services to identify areas for improvement. Consult the “Optimize INP” guidance on web.dev for best practices on enhancing interaction responsiveness.
Additionally, update any performance monitoring tools or custom scripts that rely on the deprecated FID metric to use INP instead. Be prepared for the breaking change in version 5.0 of web-vitals.js. If you leverage the CrUX BigQuery dataset, plan to update data pipelines to handle the schema changes, removing FID fields after the 202409 release in October.
By following these steps and embracing the transition from FID to INP, developers can ensure a smooth migration and optimize their websites for a more responsive user experience. This update from Google Chrome underscores the importance of staying current with evolving web performance metrics to deliver the best possible user experience.