First Input Delay (FID) – Defined, Measured, & How to Fix

First Input Delay (FID) is the time from when a user first interacts with your page to when the page responds. A good FID value is less than 100 ms and should be based on Chrome User Experience Report (CrUX) data. There’s just one main thread, and JavaScript competes to run tasks on it. How to improve FIDIn PageSpeed Insights, you’ll see a TBT tab that has issues related to the main thread being blocked. Final thoughtsEven though FID is being replaced by INP in March 2024, it’s still worth working on improving FID.