First Input Delay (FID) is one of three key metrics analysed by the Google PageSpeed Insights tool. FID measures the time that elapses from a user’s first action, such as a click or keystroke, until the browser begins to respond to that action. The purpose of this indicator is to assess the speed of a website’s interactivity.

Why is FID important?

Along with Largest Contentful Paint (LCP) and Cumulative Layout Shift (CLS), FID is one of the key Web Vitals metrics that Google uses to assess the quality of a website. These ratios are designed to ensure a good user experience, and sites with low FID values are more likely to rank higher in Google’s search results.

How is FID measured?

FID is measured in milliseconds and describes the delay between user interaction and page response. The shorter the FID time, the better. Here are the general guidelines for FID values:

  • Good: less than 100 ms
  • To be improved: 100-300 ms
  • Bad: above 300 ms

Factors affecting the FID

Some factors can affect the FID value, such as:

  • Heavy JavaScript blocking the main browser thread
  • Large number of interactive elements that require event handling
  • Slow network queries

How do you improve the FID on your site?

Here are some tips that can help you improve your FID values:

  1. Optimise your JavaScript code: Consider minimising, delaying loading or asynchronously loading JavaScript.
  2. Using Web Workers: Allows tasks to run in the background without blocking the main thread.
  3. Reducing the number of web requests: Using techniques such as caching, compression and lazy loading can help reduce page load times.


First Input Delay (FID) is an important indicator in the context of assessing the quality of a website. Improving the FID value can contribute to better page interactivity, which in turn translates into better positioning in Google search.

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