Core Web Vitals are a set of metrics defined by Google that evaluate the user experience on a web page. These metrics focus on key aspects such as loading, interactivity, and visual stability of a site. Since May 2021, Google has integrated these metrics into its ranking algorithm, meaning that sites that optimize their Core Web Vitals can achieve better positions in search results. Below are the three main metrics that make up the Core Web Vitals: LCP, FID, and CLS.
Largest Contentful Paint (LCP)
LCP measures the time it takes for the main content of a page to load. In other words, it evaluates how long it takes for the user to see the most important content on the page. To provide a good user experience, the LCP should occur within the first 2.5 seconds of the page starting to load. A good LCP ensures that users can quickly interact with the page's content, which is crucial for retaining their attention and reducing the bounce rate.
First Input Delay (FID)
FID measures the time from when a user first interacts with a page (e.g., clicking a link, pressing a button, etc.) to when the browser responds to that interaction. It is essential for evaluating the page's interactivity. An FID of less than 100 milliseconds is considered good. A low FID is crucial for the user experience because a page that responds quickly to interactions can prevent frustration and improve user satisfaction.
Cumulative Layout Shift (CLS)
CLS measures the visual stability of a page and refers to the amount of unexpected layout shift of the visual content. These shifts can occur when additional resources load on a page, such as images, videos, or ads, altering the position of visible content. A good CLS should be less than 0.1. Minimizing CLS is important to avoid frustrating experiences, such as when a user is about to click on something, and the page shifts unexpectedly, causing accidental clicks and a negative experience.
Importance of Core Web Vitals
Core Web Vitals are fundamental because Google uses them as ranking factors in its search engine. This means that websites that do not optimize these metrics may lose positions in search results, which could reduce their visibility and organic traffic. Besides their impact on SEO, Core Web Vitals are crucial for user experience. Studies show that pages that load quickly and are stable and interactive retain users better, increase the time spent on the site, and improve conversion rates.
How to Improve Core Web Vitals
To optimize LCP, several techniques can be applied, such as optimizing images, improving server response times, and using an efficient caching service. To reduce FID, it is advisable to minimize the use of JavaScript and break long tasks into smaller tasks so that the browser responds more quickly to user interactions. To improve CLS, it is essential to set dimensions for all multimedia elements (images, videos, etc.) and avoid inserting dynamic content that does not reserve adequate space.
