What is FID
The First Input Delay or FID is an indicator we use to evaluate the delay between two moments. The moment when the user interacts with an element of the site and the moment when the browser is able to respond to this interaction. In other words, it is the moment when the web page “loads” but when the user clicks a link or an image for example, nothing happens. This metric therefore focuses on the user and his expectation following their interaction. Here are some pointers on what FID is and whether to consider it in your SEO strategy.
FID measurement and score
We measure FID in milliseconds. Three scores are possible for the Google algorithm: Good, in green color; Needs Improvement, in the orange color; and Poor, in the color red. Depending on the score, the penalty for the moment is minimal. However, it speaks for itself. The poorer your FID score, the less interactive your site. The lower your bounce rate and your conversion rate. A good FID score is between 0 and 0.1 seconds (or 100 milliseconds). This means the precision and the speed. A bad FID score is around or over 300 milliseconds (or 0.3 seconds).
How to optimize it
To understand how to improve FID, we need to understand how the JavaScript code executes. The browser executes the JavaScript code sequentially. That is, it processes one piece of code at a time. This is why JavaScript is mono-threaded, because when one piece of code is running, it “blocks” other tasks. To improve the response time and boost the loading speed of the page concerned, you need to find suitable solutions.
Other solutions
Since the first cause of FID is the disordered loading of resources on a page, the first thing to do is to organize these loads. Use HTML attributes to control how a script is loaded; optimize images by loading the image in the exact size that it should be displayed according to the media; or suppress the loading of unused scripts on the page that your favorite CMS or your developer makes load on all pages for convenience.
Remember: The lower the FID, the faster the page can be used and the better impression users will have of your site.