What Is First Input Delay

What Is First Input Delay and How to Optimize It

Google constantly and continuously changes algorithms and requirements of ranking factors in order to ensure that users get the best possible user experience and relevant information. Google recently announced a new Google Page Experience ranking signal, and one of the Core Web Vitals metrics is First Input Delay (FID).

If you do not know what the Google Page Experience Update and Core Web Vitals are yet, read about it in our previous blog.

If you are interested in other metrics of the new algorithm, then you can read about them here:

Today the Wishdesk website development agency focuses on the importance of First Input Delay (FID for short) and how this can be optimized to improve the interactivity of the site.

What is the First Input Delay?

First Input Delay (FID) is one of the third Core Web Vitals real-user metrics that measure the time it takes to process a user's first interaction with a page. It is needed to measure the interactivity of a page. These are the milliseconds between the first click, taps, keypresses of the user and to the time when the site responds to the interaction.

  • Google approved this metric and started using it in 2018.
  • FID score does NOT include scrolling and zooming.
  • FID is measured in milliseconds.

Let's simulate the situation.

You have entered the site, and the page that you uploaded seems to have been loaded, but the site does not respond to anything else you do. Most likely, you will leave the site, and the site owner loses a client.

Most importantly, this metric cannot be modeled. It all depends on user behavior and how long it takes to complete the action. Why is FID such an important metric?

Because this is the first impression and interaction users have with your site. And the first impression is important.

What is the First Input Delay?

What is FID in SEO?

FID optimization is another way to improve your site for visitors and to improve SEO rankings. If your site does not answer for a long time and does not allow interaction, then users will leave it. This has a negative effect on your rankings. Any clickable element should be processed quickly by the browser.

FID is used by search engines to measure a user's first impression and site browsing experience. Therefore, if you are worried about your SEO, you can use our on-page optimization checklist.

What causes the First Input Delay?

Input lag occurs because the main browser thread is busy doing something else, so it doesn't respond to the user. A slow FID most often occurs because the site is waiting for JavaScript and/or CSS elements to load. Everything seems to be working, the content has loaded, but the page cannot yet respond to the user's request.

Let's take a look at the top 3 reasons for a bad FID score.

Reason # 1. Heavy JavaScript

Large JavaScript bundles are often the main reason for slower page response times. The user has to wait for the page to load all JavaScript.

Reason # 2. A long-running task in JavaScript

If your site has poorly optimized code or coding mistakes, then this can delay the client's request and increase the FID score.

Reason # 3. Unused JavaScript

Using unnecessary JavaScript will increase the first input delays, so it takes time to load. Get rid of unused JavaScript bundles.

What’s a good FID score?

Good First Input Delay scores:

Ideally, the FID score should be below 100 ms. If your site has this kind of score, then your site will load instantly for users.

Needs Improvement First Input Delay scores:

The average time is between 100ms and 300ms. At this rate, visitors will need to wait for a little, but this should not anger them.

Poor First Input Delay scores:

If your site requires above 300ms, then things are bad for you. You should take immediate action to optimize and improve your site's FID. Otherwise, you will lose both site visitors and SEO positions.

What’s a good FID score?

How can you measure FID on your page?

Measuring FID is somewhat different from the process of measuring all other Core Web Vitals. The main difference is that it's recommended to track it using field tools. This means that in order to get real data, real users should interact with your web pages.

Best tools to measure First Input Delay, suggested by Google

1. Chrome User Experience Report

Chrome User Experience Report is a report that helps developers improve website usability. It is a set of key usability metrics based on user data.

2. Search Console Core Web Vitals Report

The Core Web Vitals report in Google Search Console summarizes how a site has met the Core Web Vitals criteria over the past 90 days.

3. The web vitals JavaScript library

This is a minimalistic library built for front-end monitoring. This tool is the most effective today, as it allows you to track performance over short periods with very high accuracy.

4. PageSpeed Insights

PageSpeed Insights service works to audit the performance of a single URL quickly. It includes Core Web Vitals data for this page.

5. Lighthouse in DevTools: Total Blocking Time (TBT) Feature

With the help of Lighthouse, you can evaluate the importance of loading speed, and interactivity and get recommendations on how to improve the user experience.

Now that you've learned how the First Input Delay track is, it's time to learn how to optimize it. Read on to learn all the secrets of improving the First Input Delay score.

How to improve First Input Delay?

If the FID is not good, then you should take action. Want to know how you increase the first input delay? Then stay with us and find the answer to your question.

  • Optimize third-party scripts

Optimize all third-party scripts such as social media buttons, analytics, and advertising so that they DO NOT increase your website load time. Alternatively, you can use lazy loading for the scripts you need.

  • Accelerate JavaScript

Another useful tip is to break down long-running tasks into smaller ones. In the intervals between the processing of THESE short tasks, the browser will time to optimize the user's request.

  • Minimize out-of-use polyfills

If you have polyfills that you DO NOT use on the site, then remove them. A polyfill is a piece of code that is needed for the site to work properly on older browsers.

Leave only the polyfills you want.

  • Optimize CSS code

In brief, to improve your FIDs, minify, compress, and remove unused CSS is recommended.

  • Use proved WP themes and plugins

If you are using a WordPress site, then the most important advice for you will be to use only high-quality and safe WP themes and plugins. Delete the plugins that are not important. This often has a big impact on the First Input Delay score.

  • Run long tasks off the main thread

This is to carry the main thread idle and therefore increase the first input delay. To do this, you can transfer your data to a Web Worker.

  • Defer Unused JavaScript

Configure downloads of only the code that is necessary for work. Not sure which Java code matters? In the Chrome DevTools Coverage Tab, you can find the part of JavaScript code that you don't need to use.

  • Caching

With the help of caching, you can store previously downloaded content, and it will not be downloaded again when the user visits it again. Loading from a cache minimizes server load and improves performance.

  • Optimize images

By themselves, images do not affect the unresponsive direction of the page. However, the use of lazy-loading allows you to free up valuable bandwidth, which can be used for code transferring. Depending on which CMS your site is on, you can additionally use convenient quivers. Drupal image optimization will speed up your Drupal site, and WordPress image optimizers are useful for WordPress site owners.

How to improve First Input Delay?

Why you should improve First Input Delay (FID)

First Input Delay shows how quickly the client's request is fulfilled after they arrive at your site. The lower the FID rate is, the easier it is to use your site.

Optimize and improve your FID score to match Core Web Vitals and bring a better user experience to your visitors. Get help with Core Web Vitals at our web development experts.


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