What Is First Input Delay (FID): 4 Tips To Optimize It

Do you want that when a new visitor lands on your website, then when his first interaction with your web page, then he gets a good experience from your web page? If yes, then for that you first need to know about First Input Delay.

The purpose of the Chrome User Experience Report is to help the web community understand the development and delivery of users’ performance. Till now Google was focusing only on FCP and OL of page load metrics, but now Google is going to include a new user-centric metric in its algorithm.

First Input Delay FID

It focuses on the interactivity of new metric web pages: first input delay (FID). In addition, this new metric will tell Google that interactivity with the web pages of which websites of users is good.

FID has been added to Chrome just a few months ago as the original test. If you understand FID well then it is very good for your website. For a better understanding of FID, my article (What Is First Input Delay (FID): 4 Tips to Optimize It) can help you a lot. 

What Is First Input Delay (FID)?

The first input delay (FID) is a metric that measures the delay between the time a user tries to interact with the web page of your website for the first time (meaning when they click on a button, or someone Click on the link, or Javascript powered control) and that time the browser is also able to reply. This interaction between user and browser is measured in milliseconds

What Is A Good First Input Delay Score?

As you know how much Google cares about the experience of its users. Therefore, he also changes his algorithm from time to time to give a good experience to his users.

This time Google is going to change its ranking factor. The name of this new metric is First Input Delay. Just like you have to go upstairs, what is First Input Delay, but have you ever thought about what should be a good FID score? No, let me tell you that the FID of any web page of your website will be considered good only if your page opens in 100 milliseconds or less when users click on it the first time itself.

If users click on your web page and take more than 100 milliseconds to open, your web page is placed in the improvement and poor category. Like:

  • 100 millisecond or less is considered good,
  • 100 – 300ms needs improvement,
  • More than 300ms is considered poor.

How To Measure First Input Delay?

First Input Delay (FID) is a metric that can be measured only in the field and not in the lab. Because a real user is needed to check FID, therefore it cannot be done in the lab. But total blocking time (TBT) can be measured in the lab. 

Here the relation of TBT with FID is very good. TBT together with FID also captures the issues that affect interactivity. For your convenience, I have given the names of tools related to the field. With the help of which you can measure the FID. The names of these tools are as follows: 

Field tools

  • PageSpeed Insight
  • Search Console (Core Web Vitals report)
  • Chrome User Experience Report
  • JavaScript library

Measure FID by using JavaScript

You can measure FID very well using JavaScript. You have to use the Event Timing API to measure the FID. And with this help, you can also easily create a PerformanceObserver.

You can calculate the delay of FID in PerformanceObserver. But let me tell you one thing that measuring FID in JavaScript is very complicated. 

Why Is FID Important?

First Input Delay plays a very important role in finding users’ experience for Google. FID informs Google that when a user clicks on the link of a web page, then in how long the web page is open in front of the user. Here First Input Delay refers to the interaction of users with the web page. 

Those bloggers, who write a blog, know very well that when users are searching on a topic, they need an answer to their question quickly. And so they also optimize their web pages for FID.

When a user interacts with the pages of a website for the first time and if he gets a good experience from that website, then he visits the same website again and again. Because the human brain is such a system that creates an overall view and creates an opinion through the first impression. If he gets the right information from the website, in his view, that website becomes reliable and of good quality.

After loading both First Input Delay and Input Delays, they become different words for page speed science. Thus separating these two helps both SEO and developers to analyze FID more. 

What is the reason for a slow First Input Delay?

JavaScript is the main reason for slow first input delay. Because of this, the browser takes time to respond. Below I have tried to explain to you in two ways how JavaScript slows down the FID.

1. Cause Heavy JavaScript Payloads

Slow First Input Delay is possible only when the main thread of the browser is loaded before the page content is loaded and then it gets busy executing and parsing heavy JavaScript. After that, the result is when the user tries to interact with the content that appears on the page, then the browser is not able to give any reply at that time.

2. Cause Long-Running JavaScript

Another reason for Slow First Input Delay is long-running JavaScript. When JavaScript continues to load for a long period, user input is blocked. The reason for this can be any poorly optimized code. Such as Angular or React

How To Optimize FID: 4 Tips

If you want your website’s FID score to be 100 milliseconds or less, then for that you must first optimize your page for the FID. I have given below 4 tips for your help, which will be very useful for you. These tips are as follows;

1. For Optimize Use Web Workers

To optimize your web page for FID, you must use web workers. Because these web workers will give you complete freedom to run scripts in the background without breaking the main thread. It may be a good practice to move non-UI operations to the background thread. 

2. Do Not Use Non-Critical Third-Party Script In Header

You have to research all the pages of your website to see which of your web pages is being liked more by the users and then you have to give more importance to the same web page. One thing that you have to keep in mind is that you do not have to put non-critical third-party scripts like (ads and pop-ups) in the header. If possible, you remove it. 

3. Remain inactive until necessary

This is a coding strategy that allows the code to run when requested during idle periods. You will find more information about this in Philip Walton’s article. If you want, you can also see it in the idle-urgent library of npm. 

4. Remove Unused JavaScript

To optimize the FID, first, remove the unused part of JavaScript. With Minification, you can remove unnecessary parts in JavaScript such as spaces, comments, and line breaks.

Conclusion: What Is First Input Delay (FID): 4 Tips To Optimize It

You know very well that the first impression is the last and it is very well applicable for websites. This is very important for both the situation when interacting with new users and creating experiences on the web.

If your website’s pages are opened in front of users without any delay the first time, it increases the chances of visitors to your website.

Google takes the help of FID to know the experience of its users. FID informs Google how the interaction of users from the page of a website has been.

If the FID score of your page is 100 milliseconds then it is considered good. You can measure FID in many ways. For this, you will need field tools. Most important, you must optimize your page for FID. With this, the FID score of your page will always be good.

With this, I hope that my article (What Is First Input Delay (FID): 4 Tips To Optimize It) will work for you. 

FAQ: What Is First Input Delay?

I have noticed many such bloggers are still worried about FID, so they keep asking a lot of questions related to FID on the Internet. Here I am going to answer 3 important questions asked by you.

Q1. How can you fix input delay?

Ans. First, you set your monitor,

Choose a monitor that is low display lag,

Turn on pc mode or game mode on your monitor, along with it, also save power settings in it,

Turn off all post-processing options and HDMI CEC in your monitor.

Q2. How can you increase the first input delay?

Ans. You can increase First Input Delay through idle until urgent. Because the code execution in it is the most important. By this, you can reduce the main thread blocking time.

Q3. What is Max’s potential first input delay?

Ans. Max potential first input delay means when a user clicks a link to a page of your website and your page opens in front of it as long as possible. It measures the worst-case first input delay.

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