What Is FID (First Input Delay)? And Why It Was Replaced

FID stands for First Input Delay and measured how quickly a page responded to a visitor’s first interaction, for example the first click on a button or link. For years it was one of Google’s three Core Web Vitals and therefore a signal that carried weight in your SEO. One thing to know right away: FID has since been replaced. On 12 March 2024, INP (Interaction to Next Paint) took over from FID as the official Core Web Vital (web.dev). In this article you will read what FID was, why it disappeared and what you should measure today.

What exactly was FID?

FID measured the delay between the moment a visitor first interacted with a page and the moment the browser could start processing that interaction. If you click a button while the browser is still busy loading, you feel a brief stutter. That stutter is precisely what FID captured.

The metric deliberately had a limited scope. FID looked only at:

• the first interaction on the page, not later ones;
• only the input delay (the wait before processing began), not the processing time itself or the time until the screen updated.

As a result, FID gave an incomplete picture of how responsive a page truly felt. A page could post a perfectly fine FID and still respond sluggishly to everything that came after the first click.

Why was FID replaced by INP?

Google introduced INP as the successor because it fixed FID’s shortcomings. Where FID measured only the first interaction and only the waiting time, INP looks at responsiveness across the entire visit (Google). INP measures:

• every interaction on the page, not just the first;
• the full interaction: input delay, processing time and the time until the next paint (the moment the screen responds).

INP therefore gives a far fairer picture of how fast a page feels in real use. The official switch happened on 12 March 2024. From that moment FID was pulled from Google Search Console, while other tools such as PageSpeed Insights were given a transition period. That makes FID a historical metric: you will still come across it in older reports, but it no longer counts.

The table below puts the two side by side, so you can see at a glance why INP is stricter and paints a more realistic picture of responsiveness.

If you want to dig deeper into the successor, read what INP is exactly. The thresholds and improvement points are fully worked out there.

What should you measure today instead of FID?

The answer is simple: INP. INP sits alongside LCP (loading speed) and CLS (visual stability) in the current Core Web Vitals. The thresholds for INP:

• Good: under 200 milliseconds
• Needs improvement: between 200 and 500 milliseconds
• Poor: above 500 milliseconds

Just as with the other Core Web Vitals, this is measured at the 75th percentile of your visitors, split across mobile and desktop. If you still run into reports or old checklists that talk about FID, mentally replace them with INP.

How do you improve your responsiveness (INP)?

Because INP is the successor, today’s responsiveness work means INP fixes. In broad strokes:

• Limit heavy JavaScript. Long tasks block the main thread and slow down every interaction.
• Break tasks up. Split heavy operations into smaller chunks so the browser can respond in between.
• Remove unnecessary scripts. Every tracker or widget running along can delay interactions.
• Prioritise what the visitor is doing. Load non-essential things later, or not at all.

You will find a broader approach to speed and responsiveness in improving Core Web Vitals.

Honestly: how much does this matter for B2B?

Let us say it as it is: Core Web Vitals, whether FID or INP, are just one signal among many. Content and relevance weigh more heavily. You will not overtake your competitor purely because your INP score is good.

Where it does count is user experience and conversion. A B2B visitor who wants to request a quote on a sluggish page drops off faster. And practically, the most important lesson today is this: do not waste time optimising FID. It is in the past. Measure and improve INP, and only because it gives your visitor a smoother experience, not to make a number in a dashboard look better.

Frequently asked questions

Does FID still exist? As a metric you may still come across it historically, but as a Core Web Vital, FID was replaced by INP on 12 March 2024. It has been removed from Google Search Console and no longer counts as a ranking signal.

What is the difference between FID and INP? FID measured only the waiting time of the first interaction. INP measures every interaction and the full duration, including processing and rendering time, and therefore gives a fairer picture of responsiveness.

What is a good INP score? Under 200 milliseconds is good, between 200 and 500 needs improvement and above 500 is poor, measured at the 75th percentile of your visitors.

Should I still optimise for FID? No. Focus on INP, the current responsiveness metric. If you come across old checklists that mention FID, treat them as outdated.

Wondering whether your site responds fast enough?

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