Core Web Vitals: What They Are & How to Improve Them

By Carlos Calle

The internet isn’t just a stage for hosting websites; it’s a dynamic place where speed, responsiveness, and visual stability significantly shape a user’s experience. Among the multitude of metrics used to measure website performance, Google’s Core Web Vitals stand out, becoming a quintessential indicator of web health and a vital piece of Google’s ever-evolving algorithm.

Before delving deeper, it’s fundamental to start by understanding that Core Web Vitals are a set of specific factors that Google considers important in a webpage’s overall user experience. They consist of three specific page speed and user interaction measurements: Largest Contentful Paint (LCP), First Input Delay (FID), and Cumulative Layout Shift (CLS). Each of these elements individually reflects a bird’s eye view of your page’s health, for example:

  • Largest Contentful Paint (LCP) measures loading performance. It represents the time it takes for the main content on a page to load — the quicker, the better. An optimal LCP measurement is 2.5 seconds or faster.
  • First Input Delay (FID) quantifies interactivity. This metric reflects the time from when a user first interacts with your page (e.g., clicking a link or tapping a button) to the time when the browser responds to that interaction. An optimal FID is less than 100 milliseconds.
  • Cumulative Layout Shift (CLS) examines visual stability. This element checks if page elements are stable as the page loads or if they’re moving around, causing a jarring user experience. An optimal CLS score is less than 0.1.

With these fundamentals under our belt, we can now look at strategies to improve these Core Web Vitals.

  1. Speed Up Your LCP: The key here is to prioritize loading the most significant elements first. Remove any unnecessarily large page elements, optimize and compress images, use lazy loading for offscreen images, and preload important resources. Eliminating render-blocking JavaScript and CSS also ensures that your main content loads promptly.
  2. Reduce Your FID: The main issue that prolongs FID is heavy JavaScript execution. To reduce this, break up Long tasks into smaller, asynchronous tasks with the help of web workers. Defer or asynchronously load JavaScript, and consider using a web worker to run JavaScript on a background thread.
  3. Stabilize Your CLS: To maintain visual stability, ensure that all elements have set size attributes and that ads or embeds have reserved space. Avoid inserting new content above existing content unless it’s in response to user interaction.

Keep in mind that Core Web Vitals are not the only metrics that shape user experience. Complementing these are other notable metrics: First Contentful Paint (FCP), Interaction to Next Paint (INP), and Time to First Byte (TTFB). Though not part of the core vitals, they offer valuable insights about your webpage’s performance, for example:

  • First Contentful Paint (FCP) measures the time from when the page starts loading to when any part of the page’s content is rendered on the screen. A good FCP lies under 1 second.
  • Interaction to Next Paint (INP) gauges the time from a user’s interaction to the resulting visual change. A lower INP signifies a webpage that promptly visualizes user interactions.
  • Time to First Byte (TTFB) quantifies the time from a user’s HTTP request to the first byte of the page received by the user’s browser. An optimal TTFB is under 200 milliseconds.

Let’s further enrich our strategies for optimization by incorporating steps to improve these supplementary vitals.

  1. Enhance Your FCP: Improving server response times, route-based code splitting, and deferring non-critical CSS and JavaScript can all enhance your FCP. Also, preloading critical assets ensures they’re ready when needed.
  2. Boost Your INP: To optimize INP, focus on your JavaScript. Asynchronous loading, reducing execution time, and properly using interaction-ready events are good starting points.
  3. Decrease Your TTFB: Enhancing your server’s software and hardware, implementing a CDN, optimizing server-side rendering, and utilizing HTTP/2 can all reduce your TTFB significantly.

By understanding and addressing both the Core and these additional Web Vitals, you get a comprehensive picture of your site’s health and performance, enabling you to deliver a top-tier user experience. But why should you, as a website owner or developer, care about these Core Web Vitals?

As of May 2021, Google began considering Core Web Vitals as part of its ranking algorithm. This means that the performance of your website in these three aspects could significantly influence your visibility on Google’s search engine results page (SERP). Consequently, focusing on these aspects is not just beneficial for the user’s experience but also for Search Engine Optimization (SEO).

In summary, Core Web Vitals are the new heartbeat of user-centric web health. Understanding what they are and how to improve them is a prerequisite for offering your users an unmatched web experience, which Google duly rewards.

After all, in the internet, where users are more discerning than ever, offering a stellar experience is no longer an edge — it’s a necessity. As you create your web pages, keep Core Web Vitals top of mind. Remember, improving your Core Web Vitals is not a one-off task, but an ongoing best practice. As algorithms evolve and the user’s expectations grow, what constitutes an excellent user experience will continue to change. By staying committed to improving these vitals, you can ensure your website remains relevant, competitive, and valued by users — and search engines.

A faster, smoother, and more responsive website isn’t just about improved metrics; it’s about providing an experience that your users love and appreciate. After all, isn’t that what being on the web is all about?