Understanding FID: Why It Matters for SEO and How to Increase Your Scores

In the world of search engine optimisation (SEO), numerous factors contribute to the visibility and ranking of your website. Among these factors, user experience (UX) has become increasingly significant. One of the key metrics used to evaluate UX is First Input Delay (FID), a crucial component of Google’s Core Web Vitals. This article delves into why FID matters for your website’s SEO and provides actionable strategies to boost your FID scores.

What is FID?

First Input Delay (FID) measures the time it takes for a web page to respond to the first user interaction, such as clicking a link, tapping a button, or entering text into a form field. Unlike other metrics that assess loading speed, FID focuses specifically on the interactivity of a page. In essence, it’s about how quickly your website can become interactive after a user attempts to interact with it.

Google defines a good FID score as being less than 100 milliseconds. If your website’s FID score exceeds this threshold, users may experience a noticeable delay, which can lead to frustration and increased bounce rates.

Why FID Matters for SEO

Direct Impact on User Experience:

FID directly influences how users perceive the usability of your website. A poor FID score means that users experience delays when trying to interact with your site, which can lead to frustration and a negative impression.

Core Web Vitals and Ranking:

FID is one of the three Core Web Vitals that Google uses to assess the overall UX of a website, along with Largest Contentful Paint (LCP) and Cumulative Layout Shift (CLS). These metrics are part of Google’s page experience signals, which are used as a ranking factor in search results. Websites with better Core Web Vitals scores, including FID, are more likely to rank higher in search engine results pages (SERPs), giving them an edge over competitors with poorer performance.

Mobile-First Indexing:

With the shift towards mobile-first indexing, where Google predominantly uses the mobile version of the content for indexing and ranking, FID has become even more critical. Mobile users, who often experience slower connections and less powerful devices, are particularly sensitive to delays in interactivity. Optimizing FID can therefore lead to better mobile performance, which is crucial in today’s mobile-centric digital landscape.

Factors Affecting FID

JavaScript Execution:

One of the primary contributors to poor FID scores is heavy JavaScript execution. When a user interacts with a webpage, the browser needs to process any JavaScript on the page before it can respond to the user’s input. If the JavaScript is large or complex, this processing can cause delays, resulting in a higher FID score.

Main Thread Blockages:

The browser’s main thread handles most of the work related to loading and rendering the page, including responding to user interactions. If the main thread is occupied with tasks like parsing CSS, executing JavaScript, or rendering content, it can’t respond to user inputs promptly, leading to higher FID.

Third-Party Scripts:

Third-party scripts, such as those for ads, social media widgets, or analytics, can significantly impact FID. These scripts often run on the main thread and can introduce delays by blocking the browser from responding to user interactions.

How to Boost Your FID Scores

Improving your FID scores requires optimizing your website’s interactivity and reducing the time it takes for your site to respond to user actions. Here are some effective strategies to achieve this:

Minimize JavaScript Execution:

Code Splitting: 

Break down your JavaScript into smaller, more manageable chunks that can be loaded as needed. This reduces the amount of JavaScript that needs to be processed at any given time, leading to faster response times.

Defer Unused JavaScript: 

Delay the loading of non-critical JavaScript until after the main content has loaded and the page is interactive. This prevents the main thread from being blocked by unnecessary scripts.

Use Web Workers: Offload heavy JavaScript tasks to web workers, which run on a separate thread from the main browser thread. This helps to keep the main thread free to handle user interactions more quickly.

Optimize Third-Party Scripts:

Lazy Loading: 

Implement lazy loading for third-party scripts, such as ads or social media widgets, so that they only load when needed. This reduces the initial load time and frees up resources for more critical tasks.

Asynchronous Loading: Ensure that third-party scripts are loaded asynchronously, meaning they don’t block the main thread while they load. This allows the browser to continue rendering the page and responding to user inputs while the scripts are being loaded in the background.

Remove Unnecessary Scripts: 

Regularly audit your website’s third-party scripts to identify and remove any that are no longer needed or are underperforming. This helps reduce the load on the main thread and improves FID.

Reduce Main Thread Work:

Optimize CSS: 

Minimize the use of complex or large CSS files, which can block the rendering process and delay interactivity. Consider using critical CSS, which only loads the CSS needed for the above-the-fold content, with the rest loaded asynchronously.

Reduce Render-Blocking Resources: 

Identify and defer any render-blocking resources, such as large fonts or images, that may be slowing down the main thread. This allows the browser to prioritize the loading of critical content and user interactions.

Implement Server-Side Rendering (SSR): 

Use server-side rendering to pre-render the content on the server before sending it to the browser. This reduces the amount of work the browser needs to do and speeds up the time to interactivity.

Use Performance Monitoring Tools: 

Regularly monitor your website’s FID scores using tools like Google’s PageSpeed Insights, Lighthouse, or Web Vitals. These tools provide insights into what might be causing delays in interactivity and offer suggestions for improvement.

Test on Real Devices: 

Conduct performance tests on real devices, particularly mobile ones, to get an accurate picture of how your website performs in real-world conditions. This helps you identify and fix issues that may not be apparent in simulated environments.

Conclusion

First Input Delay (FID) is a critical metric that directly impacts your website’s user experience and SEO performance. By understanding what FID is and why it matters, you can take steps to optimise your website’s interactivity and improve your FID scores. By minimising JavaScript execution, optimising third-party scripts, reducing main thread work, and regularly monitoring your performance, you can create a faster, more responsive website that not only delights users but also ranks