This measurement is taken from whatever interactive element the user click on first. This is especially important on pages where the user nes to do something, because that's when the page becomes interactive. For a good user experience, the FID time should not exce milliseconds . Core Web Vitals source Japan WhatsApp Number List sweb devfid FID only focuses on input events from discrete actions like clicks, taps, and keystrokes. Interactions such as scrolling and zooming are continuous actions and have completely different performance constraints (plus, browsers are often able to hide their lag by running them in a separate thread.