Core Web Vitals: What You Need To Know

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There’s no denying it. Core Web Vitals are becoming an official ranking factor this spring. 

This means that starting in May 2021, Core Web Vitals will begin to have a real impact on your website - and whether that impact is helpful or harmful is up to your preparation. Yes, this is a big deal.

You may be asking yourself, “What are Core Web Vitals anyway?” - we’re here to break it down for you. Here is a top-level overview of exactly what you’ll need to know regarding Core Web Vital basics, so that you can ensure your website’s SEO efforts are ready to be rewarded come this May.

Why is this important?

Google has announced it will be implementing a new ‘Page Experience Signal’, which combines Core Web Vitals with the following: Mobile-friendliness, Safe-browsing, HTTPS-Security, and Intrusive interstitial guidelines. The goal of this Page Experience Signal is to encourage websites to curate more to users rather than crawlers, and create an overall better user-first experience on the web. With this signal in place, sites will be measured by their ability to meet user needs while maintaining a good status of the Core Web Vitals. Overall, if you can get it right, it’s a win-win for your website. While your Search Engine Optimists are working toward meeting Google’s new guidelines, they will simultaneously be improving the overall functionality and UX of your website, which is excellent news for you.

On the contrary, it is not yet clear on how significant of an impact poor Core Web Vitals will have on your site’s ranking in SERPs. To play it safe, we would advise you to familiarize yourself with your Core Web Vitals and try to optimize them as best as you can - doing this will only help you in the long run, and if nothing else, you will learn something new.

What are the Core Web Vitals?

So, what are the Core Web Vitals that Google will be introducing as part of their new Page Experience Signal? The following are the technical factors or official ‘vitals’ that will be used to assess your site.

Largest Contentful Paint (LCP)

Largest Contentful Paint, or LCP, represents the time that it takes for a website’s main pieces of content to finish loading. Google will place the focus on the loading time of the content on your site that is the largest in size, to evaluate the most accurate measurement of your page’s loading speed. According to Google, the LCP will be categorized as follows:

  • Less than 2.5 seconds = Good
  • Between 2.5 and 4 seconds = Needs improvement
  • Longer than 4 seconds = Bad

Takeaway: Keep your LCP at or below 2.5 seconds, and you are in the clear for this Core Web Vital.

First Input Delay (FID)

First Input Delay, or FID, represents the time it takes for your web page to be interactive with a user. In simpler terms: when a user clicks on an interactive object within your website, FID measures the time it takes for your website to respond. By Google’s standards, FID will be measured as follows:

  • Less than 100 milliseconds = Good
  • Between 100 and 300 milliseconds = Needs improvement
  • Over 300 milliseconds = Bad

Takeaway: Keep your FID under 100 milliseconds, and you are golden for this Core Web Vital. 

 Cumulative Layout Shift (CLS)

Cumulative Layout Shift, or CLS, represents the overall visual stability of your website. Simplified: when a website is loading for a user, it loads individual sections of content one at a time based on their size - CLS measures the time it takes for all elements of a web page to load completely and no longer shift in their placing. Google announced that CLS will be categorized as follows:

  • Less than 100 milliseconds = Good
  • Between 100 and 250 milliseconds = Needs Improvement
  • Longer than 250 milliseconds = Bad

Takeaway: Try to keep your CLS under 100 milliseconds and you will crush your algorithm evaluation on this Core Web Vital.

 Essential SEO Steps to Take

All this information is great, but what can you actually do with it when it comes to optimizing your website? In short: Hold yourself to Google’s new standards, and make improvements as you see fit over time. Here’s how to get started.

 Measure your Core Web Vitals

When it comes to measuring your Core Web Vitals, there are many options for tools out there. Here at Eternity, we use both PageSpeed Insights and Lighthouse. Both of these tools are easy to navigate and understand, and provide excellent insights for websites. By utilizing tools like these, you will be able to understand how your website compares to Google’s standards for LCP, FID, and CLS. From here, you can optimize accordingly.

Make Improvements

Next comes the harder part. You’ve got your stats, you understand where you stand in terms of Google’s ideal placements - but now you’ve got to actually improve. Scary. Don’t worry, each Core Web Vital has some typical simple adjustments that can have significant impact. Additionally, if you choose to use Pagespeed Insights for your analysis, the platform actually provides next steps to take to ‘fix’ each problem. Here are some typical factors for each Core Web Vital:

  • LCP: loading time for resources, client-side rendering, time for server response
  • FID: third-party code, number of server requests, JavaScript runtime
  • CLS: Image and video specific sizing, reserving space for potential on-page ads, ensuring preloaded elements do not change in size

Takeaway: Playing around with each of these factors can have a large impact on your Core Web Vital stats. Additionally, we strongly recommend trying out the suggestions made by insights platforms like Pagespeed Insights.


Ultimately, when it comes to effective SEO, there is no golden ticket to winning at SERPs. If anything stays consistent with Search Engine Optimization, it’s that trial and error is always a part of the process. With Core Web Vitals, this is surely no exception. Analyzing where you currently stand compared to Google’s recommendations is important, and optimizing accordingly is important. After that, all you can do is wait and continue to evaluate how your site is performing in SERPs. Come May, Google’s new ranking factor will be fully underway, so preparing accordingly now will only benefit you for when that day comes!


This was a lot of information, so it’s understandable to feel a little overwhelmed. Here are some key takeaways to remember as you move forward in your SEO journey:

  • Measure your Core Web Vitals, and see where you currently stand in terms of Google’s new standards
  • Optimize your site accordingly - even if that only means adjusting one thing at a time
  • Wait to see the impact, evaluate accordingly, and repeat

If you’ve got additional questions, are looking for a site audit, or just want to say hello - get in touch today! Onward and upward! 🚀

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