Google officially retired First Input Delay (FID) and completed the rollout of Interaction to Next Paint (INP) as a Core Web Vital ranking factor.
Why Google Retired FID
FID isolated only the very first touch action a user performed on load. INP computes responsiveness across the entire lifespan of a visit, identifying input delays of elements down the page.
The Three Phases of Interaction Processing
When a customer touches a button, the visual delay is measured in three parts:
- Input Delay: The time between the click action and the execution of the target event listener.
- Processing Time: The actual processing runtime required by your active JavaScript files.
- Presentation Delay: The time the rendering queue needs to draw the next frame on screen.
Optimizations to Achieve Under 200ms INP
- Break Up Long Tasks: Yield heavy computations back to the main thread using requestAnimationFrame or requestIdleCallback.
- Minimize Unnecessary Reflows: Simplify CSS hierarchy structures to prevent slow repaint calculations.
- Eliminate Third-Party Script Bloat: Avoid loading non-critical analytics codes prior to direct user action.
“Minimizing INP values guarantees a friction-free user experience as responsive and smooth as mobile native apps.”