First Input Delay (FID)
May 20, 2023
The First Input Delay (FID) is a user-centric metric that measures the time delay between when a user interacts with a website and when the website actually responds to that interaction. It is the time delay between the first user input and the browser’s processing of that input.
FID is one of many metrics used to evaluate website performance and user experience. It is particularly important because it measures the delay between the user’s action and the website’s response, which is a critical aspect of user experience. FID helps website developers identify and fix issues that may cause delays in website interactions and improve overall user experience.
Purpose of FID
The purpose of FID is to measure the user experience when interacting with a website. It is designed to capture the delay between the user’s action and the website’s response, which is a critical aspect of user experience. FID is particularly useful for measuring the performance of interactive features such as buttons, links, forms, and other user interface elements.
FID helps website developers identify and fix issues that may cause delays in website interactions. By measuring FID, developers can identify bottlenecks in the website’s code and optimize it to improve website performance and user experience. This metric is also useful for website owners who want to monitor the performance of their websites and ensure that they are providing a good user experience to their visitors.
FID is a key metric in Google’s Core Web Vitals, which is a set of metrics that measure website performance and user experience. Google uses Core Web Vitals as a ranking factor for search results. Websites that perform well on these metrics are more likely to rank higher in search results, resulting in more traffic and better visibility.
How FID is measured
FID is measured using JavaScript. When a user interacts with a website, such as clicking a button or filling out a form, the browser records the time of the interaction. The browser also records the time it takes for the website to respond to that interaction. The difference between these two times is the FID.
FID is measured in milliseconds (ms). The ideal FID is less than 100ms. A FID of 100-300ms is considered to be poor and may result in a negative user experience. A FID of more than 300ms can significantly impact user experience and may result in lower website engagement and conversion rates.
How to improve FID
Improving FID involves optimizing website code to reduce the time it takes for the website to respond to user interactions. Here are some ways to improve FID:
1. Reduce JavaScript execution time
JavaScript is a common cause of delays in website interactions. By optimizing JavaScript code, developers can reduce the time it takes for the website to respond to user interactions. This involves minimizing the amount of JavaScript code on a webpage, reducing the size of JavaScript files, and optimizing JavaScript code for faster execution.
2. Remove unused code
Unused code can slow down website performance and increase FID. By removing unused code, developers can reduce the time it takes for the website to respond to user interactions. This involves removing code that is not being used, such as unused CSS and JavaScript files.
3. Use browser caching
Browser caching can significantly improve website performance and reduce FID. By caching frequently used resources, such as images, CSS files, and JavaScript files, the browser does not need to download them every time a user visits the website. This can significantly improve website performance and reduce FID.
4. Optimize images
Large images can slow down website performance and increase FID. By optimizing images for the web, developers can reduce the size of images without compromising image quality. This can significantly improve website performance and reduce FID.
5. Use a content delivery network (CDN)
A content delivery network (CDN) can significantly improve website performance and reduce FID. By storing website resources on multiple servers around the world, CDNs can deliver website content to users from the server closest to them. This can significantly reduce the time it takes for the website to respond to user interactions.
