How to improve first input delay?

Welcome to part 3 of the mini-series on how to improve your Core Web Vital rank. In this series

Background with blue elements.

Welcome to part 3 of the mini-series on how to improve your Core Web Vital rank. In this series we dig deeper into the new ranking factor for search results that Google has announced will become official in May 2021.

In part 1: Why you need to take core web vitals seriously, we explain the basics of what Core Web Vitals are and why they have such a large impact on your online performance. In part 2: How to improve Largest Contentful Pant we give our best tips on how you can improve your LCP score, one of the three key metrics that Core Web Vitals Consists of. In this part 3, we will go through the second key metric, First Input Delay, and explain how you can improve your FID score.

Short recap, what are core web vitals?

Core Web Vitals are the latest add-on to Google’s algorithm. The new update lays a heavy focus on page experience, making it a strong ranking factor. The point behind Core Web Vitals is to encourage user-friendlier websites. Google has formerly measured user experience on sites based on more traditional metrics such as:

  • Mobile-friendliness
  • Safe browsing
  • No interstitials

Added factors that form the Core Web Vitals are:

  • Largest Contentful Pain = LCP
  • First Input Delay = FID
  • Cumulative Layout Shift = CLS

All of these metrics are taken into consideration when ranking your website, but more focus will be laid on LCP, FID, and CLS, meaning the Core Web Vitals, as these measure user-friendliness. In order to get a good rank and appear on SERPs, you better pay attention to your Core Web Vitals score.

First input delay = FID

First input delay, FID, is essentially a score of how good of a first impression your site makes. First impressions are not only important in real-life events, they are crucial also in the World Wide Web. FID measures the responsiveness of a website. When you interact with something on a webpage, click, tap or submit for example, how fast does the website interact with your action? How fast does it take for the site to process and deliver? That’s what FID measures. Keep in mind that FID only measures concrete actions such as button presses, clicks, and taps. Continuous actions such as scrolling and zooming can’t be measured with FID. If your site is mainly content browsing, the FID score will not be as crucial to you, while if your site offers a login section and is dependant on interaction from your visitors, the FID score is tremendously important. FID is a measure that is impossible to simulate in a lab, it requires real user interaction to measure, and is, therefore, an inevitable part of the Core Web Vitals.

An example of LCP

As First input delay measures responsiveness on your website, it measures the time it takes from a user’s first interaction with the website to when the browser responds to the interaction. Let’s say you have a sign-up form on your website, that your visitors fill in and submit by clicking a button. How long does it take from the moment they click the submit button, to a successfully processed request? This is your First Input Delay. If your visitors need to wait around, or even worse, press the submit button repeatedly because your site is not responding, this is a sign of a poor FID score and will harm your website performance.

Target FID score

First Input Delay is measured in milliseconds. To meet the criteria for a Core Web Vitals ranking, your page should have an FID of less than 100 milliseconds in order to be able to provide a good user experience. Remember, FID only measures the “delay” in the processing, not the processing time itself. In order to become Core Web Vitals compliant your site should hit the recommended target of 75% for each metric. This means that a site should have an FID score of 100 ms or less for 75% of their page loads in order to get a good ranking.

How to improve FID?

  • Minimize the JavaScript = this is the first thing you should look at. If you get an unsatisfying FID Score, your JavaScript is usually the one to blame. If your browsing is busy loading a large JS file, it’s impossible to interact with the site until it’s loaded. This can increase the FID and remember you want to keep the number as low as possible. There are many things you can do to optimize your JavaScript code. Use web workers, defer unused JS, use polyfills only when needed, break up long tasks into smaller ones and only send the needed code and remove everything unnecessary.
  • Remove third-party scripts = having a bunch of third-party scripts and plugins can and will make your browser slow, and the more elements you have loading simultaneously, the slower your site.  By removing unnecessary third-party scripts that you don’t need can speed up your site and have a positive impact on your FID score.
  • Reduce request counts and transfer sizes = in order for a browser to render content to a screen, all requests, CSS and JS needs to be finished first. If you have a huge amount of requests and huge files to transfer, this can delay the rendering time and slow down your site a lot.
  • Cache baby cache = by caching you store data “temporarily”, making it possible to access data locally the next time a website is visited instead of re-downloading it, again and again, every time you visit a site. This helps a lot with website speed which as you know by now, is favorable for a good FID score.

Where to pull the report?

Now that we’ve gone through the different components that Core Web Vitals Consist of, you may wonder, how will I know my current score? A very valid question at this point. Google has made it very easy for you to track your site’s ranking, they really want you to improve your site’s performance so why should they keep the report a secret. There are several ways where you can find out your ranking but the absolute simplest way is to open your Google Search Console (if you don’t have an account, make one right now) and pull open the Core Web Vitals report. This was formerly named Speed Test if you are confused about why it’s gone. You will get a full report on your status both for mobile and desktop, the rest is up to you to fix.


Key takeouts when it comes to the Core Web Vitals Metric FID is that it measures responsiveness on a webpage. How long does it take for a website interaction to successfully be processed? This is your FID score. FID only measures concrete interactions such as presses, clicks, and taps, and it’s the delay that’s being measured. The FID score needs to be less than 0.1 seconds or less across 75% of page views. FID is a huge user-experience metric as it measures interactivity and responsiveness on site. This can be the crucial first impression of a new visitor or the difference between a lead and a sale. You do not want to lose a potential customer because of milliseconds of delay. The main issue with low FID scores tends to be issued with JavaScript, so optimizing your code and minimizing third-party scripts can have a huge impact on your FID score.

Next week we will go deeper into the third and last metric of Core Web Vitals called Cumulative layout shift, CLS, a metric that measures the visual stability of a website. If you have any questions regarding Core Web Vitals, please don’t hesitate to drop us a line at and our team will be happy to answer your questions.