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First Input Delay: How Publishers Can Measure And Fix FID Issues

As digital advertising evolves, regulatory bodies, associations, and industry experts continue to emphasize the importance of focusing on user experience and privacy. As part of this user-focused approach, Google introduced its Core Web Vitals ranking signals in early 2021, making it clear that websites and publishers could find themselves penalized in SERPs if they failed the Web Vital scores, one of which is First Input Delay.

Today, optimizing for Core Web Vitals is a critical part of SEO, and First Input Delay (FID), is one of several key metrics focused on enhancing user experience and improving your site’s performance. However, despite being active for well over a year, many publishers still aren’t clear on the requirements for an acceptable FID score. 

As digital advertising evolves, regulatory bodies, associations, and industry experts continue to emphasize the importance of focusing on user experience and privacy. As part of this user-focused approach, Google introduced its Core Web Vitals ranking signals in early 2021, making it clear that websites and publishers could find themselves penalized in SERPs if they failed the Web Vital scores, one of which is First Input Delay.

Today, optimizing for Core Web Vitals is a critical part of SEO, and First Input Delay (FID), is one of several key metrics focused on enhancing user experience and improving your site’s performance. However, despite being active for well over a year, many publishers still aren’t clear on the requirements for an acceptable FID score. 

In this article, we’re going to explain:

  • First input delay and how it works.
  • What qualifies as a good FID score.
  • The causes of FID.
  • How to measure your score.
  • How to reduce first input delay.

If you’ve monetized your website, whether as a publisher or business owner, the information in this article will help you improve the overall user experience of your site, enhance your SEO, and boost the performance of your website.

What Is First Input Delay (FID)?

First impressions are everything, and that’s exactly why First Input Delay is one of the most critical metrics in Core Web Vitals. Those first few seconds on a web page are enough for a user to decide whether your website’s performance is up to par or if they’d rather visit elsewhere.

In those first few seconds, critical resources need to load, blocking the browser’s main thread. That delay, from a user first opening the page to the moment all critical resources are loaded, is called the First Input Delay.

First Input Delay is not the same as “Time To Interactive” (TTI). TTI, commonly confused with FID, measures the total time it takes for a page to become fully interactive and usable by visitors. Instead, FID tracks a user’s action before a page is fully interactive, allowing a browser to capture critical, early interactions.

Similarly, it doesn’t track event processing time. Instead, it only measures the delay in processing a user’s request, not the entire event process. In short, First Input Delay measures how long it takes to load the critical elements of a page from the moment a user first interacts with it.

What Causes First Input Delay?

There are several factors that can affect FID, including videos, images, and scripts that are unoptimized or that load in a non-orderly manner. That results in a web page pausing and reloading several times, causing the web page to become unresponsive to users while loading.

According to Google, “...input delay (a.k.a. Input latency) happens because the browser’s main thread is busy doing something else, so it can’t (yet) respond to the user.” It goes on to say that large Javascript files are one of the most common culprits of these delays. However, having several plugins and heavy WordPress themes running on a site can also have a severe negative impact on FID performance.

How To Measure Your First Input Delay

There are a few free tools available to measure your FID score. By using these tools and performing the analyses, you’ll know whether it’s necessary to reduce your First Input Delay:

Source: PageSpeed Insights Score for rev•amp

You’ll likely get different results from each tool. It’s a good idea to primarily rely on the data from PageSpeed Insights and Search Console, particularly if your goal is to improve your SEO and negate any possible penalties from Google. These two tools will show you “field data”; in other words, how users are actually experiencing your website.

What Is A Good FID Score?

Google’s Core Web Vitals divide scores into three categories:

  • Good: FID under 100 milliseconds provides a good user experience.
  • Needs Improvement: A score between 100 and 300 milliseconds indicates the need for improvement.
  • Poor: If the score is over 300 milliseconds, the site needs a lot of improvement.

If you have a “poor” or “needs improvement” score on any of the platforms we’ve indicated above, we recommend attempting to improve it using our tips below.

How To Reduce First Input Delay

Once you’ve measured your First Input Delay, you need to optimize it. There are several tactics that publishers can use to improve this part of their Core Web Vitals score. We’ve listed the best ways below.

Remove Unused Javascript Or Reduce Loading Time

There may be unnecessary third-party javascript codes running on your web page, decreasing its performance. These scripts may be executed due to plugins or custom-coded functionalities, amongst other reasons. To improve the page’s FID score, these codes need to be removed.

Alternatively, if the codes are essential to your website functioning normally, defer the script. That way, the code will load strictly when it’s necessary for a page to appear as designed or for a particular functionality to become available.

Employing an “Idle Until Urgent” strategy means that essential code is executed immediately, while other codes are only run during idle periods. That is an excellent way to improve your FID score.

Employ Lazy Loading

Lazy loading is an excellent way to increase page speed, particularly for publishers using programmatic ads. By using this strategy, ads above the fold will load first, reducing the time it takes for the site to become fully functional.

The lazy-loaded ads sitting below the fold will only load once they come into a user’s view. Not only will this improve user experience and FID score, but it will also improve the viewability scores of your ads.

Optimize And Minify Javascript

Using plugins such as Assets Cleanup, Autoptimize, WP Rocket, and others to minify javascript is an excellent way to improve your FID score and boost a site’s performance. By minifying the javascript, line breaks, comments, whitespace, and other unnecessary elements are removed from a script file. The result is a small file that renders much faster.

Conclusion

Core Web Vitals are critical ranking factors for SEO and publishers can’t afford to neglect them. First Input Delay is one of these important metrics and, if neglected, can result in severe ranking penalties for publishers. Luckily, it’s one of the easier metrics to improve, particularly if you employ the tips we’ve shared. It’s also an excellent idea to work with an ad partner that understands the vital importance of Core Web Vitals and FID and can help you employ the right strategies to keep your ads running well and your users happy.

Ferran is the Director of Catalog & Traffic at Softonic.
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