INP replaced FID because it watches the whole visit

INP replaced FID because it watches the whole visit

If you remember FID — First Input Delay — INP — Interaction to Next Paint — is its smarter replacement, official since 2024.

The difference is huge. FID only measured your first click and only the initial delay, not the full response. It was like grading a restaurant solely on how fast they greeted you at the door.

INP watches every interaction during the visit — clicks, taps, key presses — and measures the full time until the screen updates. It reports near your worst one.

1. This means a slow filter or menu used mid-session now counts.
2. You can't just optimize the first click and coast.
3. Test by actually using your site, not just loading it.

This is more honest, and a little more demanding.

Try this: interact with three different features and note which feels slowest — that's where INP is looking.