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Performance

What is FID (First Input Delay)?

Deprecated Core Web Vital that measured only the first user interaction. Replaced by INP in March 2024.

Also known as: First Input Delay

First Input Delay measured the delay between a user's first interaction (tap, click, keypress) and the browser's ability to begin processing that event. It was a Core Web Vital from 2020 to 2024.

FID is now deprecated — Google replaced it with INP (Interaction to Next Paint) on March 12, 2024. INP measures all interactions throughout a session, not just the first one, which made it a much more accurate signal of perceived responsiveness.

You'll still see FID referenced in older articles and older versions of PageSpeed Insights. Treat it as historical — INP is the metric Google now uses for ranking.

Why it matters

Most older SEO and performance content still references FID. Knowing it was deprecated saves you from optimizing the wrong metric.

Related

More Performance terms

INP (Interaction to Next Paint)

How long the page takes to visually respond to a user interaction (tap, click, keypress). Replaced FID as the official Core Web Vitals responsiveness metric in March 2024.

TBT (Total Blocking Time)

Lab-data metric that sums all the time JavaScript blocked the main thread between First Contentful Paint and Time to Interactive.

Core Web Vitals

Google's three measurements of page experience — loading speed (LCP), interactivity (INP), and visual stability (CLS). A real ranking signal since 2024.

LCP (Largest Contentful Paint)

How long it takes for the largest visible element (hero image, headline, etc.) to render. Google's primary loading-speed metric.

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