How to avoid having "FID issue: longer than 300ms" with Google Search Console?

Question

On some of my websites, Google's Search Console tool and PageSpeed show a Max First Input Delay of 300 seconds on mobile and 900 seconds on PC on my homepages.

Strange phenomenon because even on a development environment where I disable all javascript and css code, the result does not change.

Moreover, I installed on my website the following script, developed by Google: https://github.com/GoogleChromeLabs/first-input-delay

It allows you to send data to Google Analytics on the FID. On my website, I added a line in the code so that the Browser Console returns the FID (console.log(delay);).

And the result is not surprising : Less than 5 or in some cases 10 milliseconds for the browser to respond when you click anywhere on the page.

So I think that google doesn't do a simple click on the page to calculate the FID. By the way, I also know that the FID is calculated by real users on Google Chrome, it can't be done by a bot.

But in this case, how do you identify the element that could take half a second or even a whole second before the browser responds?

Despite my long researches on the internet on this subject, all give the same explanations to make a diagnosis, but this does not help me in my problem.

Answer 1

Since you already tried removing CSS and JavaScript links, you could also try:

• Taking a look at any images (img) and see how long those take to load
• Taking a look at any iframes in your site and seeing how long those take to load
• Checking how long any favicon(s) take to load
• Any dns-prefetch or preconnect meta tags.
• Taking a look at the Sources tab in DevTools to see what HTTP requests are made while loading

Sorry I couldn't be of more help in terms of specific solutions to your problem — I didn't really have much information on your specific site and what HTTP requests are made while loading it.

I hope this helps.