Understanding FID: the key to optimising your SEO strategy

Through our SEO Agency Optimize 360

on the theme : Technical SEO

In the world of Search Engine Optimisation (SEO), performance indicators are crucial for evaluating and improving the effectiveness of your actions.

One of the most important aspects to take into account is theuser experienceThese include the speed and fluidity with which your site or application loads and reacts to user interactions. FID, or First Input Delayis an essential criterion for measuring this type of performance.

In this article, we will explore in detail the definition of this indicator and how it can help you optimise your approach to SEO.


What is the FID?

First Input Delay, or FID, is a measure of how long it takes for a web page to respond to the first user interaction, such as clicking on a link, pressing a button or using a form control.

It is therefore an indicator of speed, but also of the quality of the user experience offered by your website. The lower the FID, the better the overall impression the user will have and the greater the likelihood that they will stay on your site and interact with other elements and pages.

Why should FID be an important part of your SEO strategy?

SEO is not just about achieving good positioning in search results, but also about ensuring that visitors find the information or services they are looking for quickly and efficiently. A poor user experience, particularly in terms of speed, can result in a bounce rate on your site and drive users to find alternatives with your competitors.

What's more, Google recently introduced DIF as one of the key indicators in its signal Web Vitalswhich takes into account several factors linked to the quality of a web page, such as its loading speedand its responsiveness to user interaction and visual stability.

SEO professionals therefore need to be concerned about FID in order to optimise their site, not only to offer a better user experience, but also to meet the requirements of search engines and improve their ranking in the SERP (Search Engine Results Page).

How do you measure the FID of your website?

To accurately assess your site's First Input Delay, we recommend using specific tools dedicated to this function, such as :

  • Lighthouse : Lighthouse is a tool developed by Google, integrated into its DevTools within Chrome, which allows you to analyse the overall performance of a web page, including its FID. It also provides access to advice and recommendations for optimising the quality of your site.

  • PageSpeed Insights : This other tool offered by Google analyses your site and generates a detailed report showing loading speed and problems affecting FID and user experience. PageSpeed Insights takes real user data into account, giving you an accurate picture of your site's behaviour in real-life conditions.

  • CrUX Dashboard : The Chrome User Experience (CrUX) is another solution provided by Google for tracking FID in a customised dashboard. This resource allows you to monitor the performance of your site over several periods and speed thresholds.

How can I improve First Input Delay?

Reduce JavaScript processing time

Le JavaScript is often responsible for slow web pages and high FID. This language can monopolise device resources during processing, preventing the page from responding quickly to user interactions. To solve this problem, here are a few things you can do:

    • Minimise and compress JavaScript files, to reduce their size and hence their download and processing times.
    • Move non-essential scripts to the bottom of the file HTMLor run them asynchronously (async) or postponed (defer), to minimise their impact on the initial rendering of the page.
    • Use caches to store recurring elements and speed up page loading for subsequent visits.

Optimise your CSS and image files

Like JavaScript scripts, excessive file sizes CSS and images can also impact your site's performance and increase FID. Don't hesitate to :

    • Minimise and compress CSS files to reduce their size.
    • Optimise your images by using formats suitable for the web, adjusting their dimensions and applying compression techniques without loss of quality.
    • Use a " lazy loading "(load as you scroll) for images below the waterline, to improve the initial page load time and potentially the FID.

Preventing the negative effects of custom web fonts

Using custom web fonts can give your site a unique look, but it can also lead to performance problems if they are not properly optimised. Consider :

    • Load fonts asynchronously with the font-display : swapwhich lets you quickly display text in a substitute font while the custom font loads in the background.
    • Choose modern, high-performance font formats such as WOFF2.
    • Limit the number of font variants to those strictly necessary, to avoid overloading the device's resources.

By applying these tips and bearing in mind the importance of FID for the overall user experience and search engine performance of your website, you are well on the way to optimising your SEO strategy and achieving the highest possible quality for your visitors.

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