What Is FID?
FID (First Input Delay) is a Core Web Vitals metric that measured the delay from a user's first interaction with a page (click, tap, or key press) until the browser began processing the event.
In March 2024, Google replaced FID with INP (Interaction to Next Paint) as the primary interactivity metric.
Why FID Was Replaced by INP
FID had fundamental limitations:
| Limitation | FID | INP |
|---|---|---|
| Coverage | First interaction only | All interactions during a session |
| What it measures | Delay before processing begins | Delay until the next frame |
| Representativeness | Low (the first click often happens before JavaScript runs) | High (real user experience) |
For example, a page with a good FID (a fast first click) may have a poor INP (it slows down when navigating filters).
FID Thresholds (Historical Reference)
| Rating | Value |
|---|---|
| Good | ≤ 100 ms |
| Needs improvement | 100–300 ms |
| Poor | > 300 ms |
For comparison, INP's threshold for “good” is 200 ms.
Where FID Data Still Appears
FID data is still available in:
- Google Search Console — historical data up to March 2024
- Chrome UX Report — field data from previous periods
- Older audits — PageSpeed Insights reports from before 2024
New reports and monitoring use INP.
INP: What the FID Replacement Measures
INP (Interaction to Next Paint) measures the delay from any interaction until the screen updates:
Пользователь кликнул на кнопку
↓
[Задержка INPUT] ← часть которую измерял FID
↓
[Обработка события] ← JavaScript выполнение
↓
[Рендеринг кадра] ← обновление экрана
↑
Всё вместе = INP
FID measured only the first part. INP measures the full time from a click to the screen update.
How to Improve Interactivity (INP)
The methods are the same as for FID:
- Break up long JavaScript tasks (Long Tasks > 50 ms)
- Use Web Workers for heavy computations
- Optimize event handlers
- Implement optimistic UI updates
// Оптимистичный UI: обновить интерфейс немедленно
button.addEventListener('click', () => {
button.disabled = true; // мгновенная обратная связь
button.textContent = 'Загрузка...';
// Тяжёлая операция — позже
requestAnimationFrame(() => {
processHeavyOperation();
});
});Check Web Vitals on reChecker
Use Web Vitals to measure current Core Web Vitals metrics: LCP, INP, and CLS. The tool provides real values using Puppeteer and flags obsolete FID if it appears in the data.
FAQ
Should I optimize for FID if it is obsolete? No. Optimize for INP, which has been the official Core Web Vitals metric since March 2024. If your INP is good, your FID would also have been good—they are related.
Does FID affect Google rankings now? No. Since March 2024, Google has used INP instead of FID in the Page Experience algorithm. Focus on INP.
What is TBT, and how is it related to FID/INP? TBT (Total Blocking Time) is a Lighthouse lab metric that correlates with FID/INP. It is used in PageSpeed Insights as a proxy for assessing interactivity in lab conditions (real FID/INP require users).