---
title: "What is First Input Delay (FID)?"  
description: "What is First Input Delay (FID)?"  
author: "Anubhav Sharma"  
published: 2025-04-06  
updated: 2025-04-24  
canonical: https://www.mindstick.com/forum/161440/what-is-first-input-delay-fid  
category: "web development"  
tags: ["web development"]  
reading_time: 2 minutes  

---

# What is First Input Delay (FID)?

What is [First Input Delay](https://www.mindstick.com/blog/304957/the-growing-importance-of-core-web-vitals-for-seo-rankings) ([FID](https://www.mindstick.com/forum/161445/how-is-inp-different-from-fid-and-why-is-it-preferred))?

## Replies

### Reply by ICSM Computer

**First [Input](https://www.mindstick.com/forum/159209/how-can-i-read-convert-an-input-stream-into-a-string-in-java) Delay (FID)** is a web performance metric that measures the time from when a user first interacts with your site (like clicking a link, tapping a button, or using a custom JavaScript-powered control) to the time when the browser is actually able to begin processing that interaction.

### Key Points:

1. **FID measures delay** — not the total time it takes to process the event, just the delay before the event handler starts executing.
2. It captures **real-user interaction** latency — only the *first* interaction counts.
3. FID is important because it reflects the site’s **responsiveness** from the user’s perspective.

### Why FID Happens:

The most common cause of high FID is the browser's **main thread being blocked** — often by long JavaScript tasks — preventing it from responding to user input.

### Ideal FID:

1. **Good**: < 100 milliseconds
2. **Needs Improvement**: 100–300 milliseconds
3. **Poor**: > 300 milliseconds

### Example:

If a user clicks a button, but the main thread is busy running a large script and can’t handle the click until 400ms later, the FID would be **400ms**.

### Note:

Google is replacing FID with **Interaction to Next Paint (INP)** as a more comprehensive responsiveness metric in **March 2024**, since INP reflects the responsiveness of all interactions, not just the first.


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Original Source: https://www.mindstick.com/forum/161440/what-is-first-input-delay-fid

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