FID stands for First Input Delay. It is an important measure of web performance, which records the time it takes for a webpage to respond to the first interaction from a user, e.g. when they click a button or a link. FID is part of Google's Core Web Vitals, which assess how a website performs in terms of user experience. A low FID means that the page is quick to respond to users' input, which is crucial for a positive user experience and good SEO.
How does FID work?
FID measures the delay between a user's first action (e.g. a click or a press) and the moment the browser begins to respond to this action. A long delay can frustrate users, as they expect the page to respond quickly to their input. FID is measured in milliseconds, and Google's recommendation is that FID should be under 100 milliseconds to ensure a good experience.
What affects FID?
Several factors can affect a page's FID:
- Heavy JavaScript files: If the browser is busy loading and processing JavaScript, it can delay how quickly it responds to user input.
- Rendering: Complicated layouts or graphical elements can delay the browser's ability to register input.
- Network issues: A slow connection or poor server response can also extend input delay.
Why is FID important?
A low FID ensures that users can quickly interact with a page without frustration. From an SEO perspective, FID is important because Google considers the user experience as part of their ranking. A page with a high FID can be penalized in search results, as it indicates a poor user experience. Good performance in FID is especially important for interactive elements on pages such as e-commerce platforms and applications.
How can you improve FID?
To reduce FID and make your page more responsive you can:
- Optimize JavaScript: Reduce or defer non-essential JavaScript files, so the browser can focus on user input.
- Lazy loading: Load the essential content first and save heavy elements for later.
- Use browser caching: Store frequently used files in the browser so they don't need to be reloaded.
A fast response time is crucial for both user experience and your site's SEO results, and FID plays a central role in ensuring this performance.