Core Web Vitals Deconstructed: LCP, FID & CLS

Google recently made headlines when it announced a new ranking factor for 2021: page experience. User experience has always been a crucial component in creating the best site possible, but it will now play an even bigger role in assisting you in creating amazing sites for your customers. All of this is fueled by new metrics, the most important of which is the Core Web Vitals. It’s time to get to know LCP, FID, and CLS!

The Google page experience update powered by Web Vitals

We’ve already discussed this page experience update, but we’d like to go over the Core Web Vitals again. In general, site speed metrics are difficult to comprehend and decipher. Furthermore, they appear to shift slightly each time you test your web. It’s not always possible to get the same results. It’s safe to suggest that you just have to keep an eye on some numbers and hope they turn green.

Google has identified three “Core Web Vitals” out of all the possible metrics. In the coming year, these will be Google’s main focus. Google may add or update these metrics every year as they evaluate them over time.

The subset of Web Vitals that apply to all web sites, should be assessed by all site managers, and will be surfaced across all Google tools is known as Core Web Vitals. Each of the Core Web Vitals represents a unique aspect of the user experience, is field observable, and demonstrates real-world experience with a crucial user-centric outcome.

The three foundations of page experience are,, and

For the time being, these are the three foundations of page experience:

Output during loading (how quickly does information appear on the screen?)

The responsiveness of the page (how quickly does it react to user input?)

Visual stability (does the content on the computer shift around as it loads?)

Google selected three corresponding metrics — dubbed the Core Web Vitals — to calculate these critical aspects of user experience:

LCP, or Largest Contentful Paint, is a metric that calculates how long it takes for the largest piece of content on the screen to appear. This may be a picture or a paragraph of text. A high rating gives users the impression that the web loads quickly. A sluggish website can be aggravating.

First Input Delay, or FID, is a metric that measures how long it takes for a website to react to the first contact. This may be anything as simple as pressing a button. A high score here indicates that a site is easy to respond to user feedback and, as a result, sensitive. Slowness, once again, is a source of irritation.

CLS, or Cumulative Layout Change, is a metric that tests the site’s visual stability. To put it another way, does something move around on the screen as it loads, and if so, how often? There’s nothing more aggravating than having to press a button when a slow-loading advertisement appears in the same place.

According to Google’s John Mueller, if you want your site to rank higher, all three metrics must be green. Of course, you shouldn’t optimise your site for green scores; however, getting green scores will undoubtedly benefit your guests. It’s all about happy guests — and, of course, great stuff! While the Page Experience update is on the way, it is unlikely to have a significant effect right away. According to Google’s Danny Sullivan, it will be implemented progressively and could become more relevant over time.

Different tools use different metrics

Any page experience tool makes use of a number of Web Vitals collected from various sources. Since each method serves a particular function, the metrics used vary. The Core Web Vitals, which Google uses in any page experience tool it has, are the common denominator.

But what do both of these figures imply? What should you be looking for on your website? When will your website be quick enough? When am I going to get a decent grade? There are a slew of questions that could be asked about these figures. And, although Google is working to bridge the gap between awareness and improvement, this is still a difficult subject to grasp. Measuring site speed and user experience is difficult because there are too many variables to consider.

What are these Core Web Vitals?

There are several other indicators in addition to the Core Web Vitals, so they don’t function in isolation. Some metrics are based on controlled lab measurements, while others are based solely on field results. Google came up with a new collection of metrics called Web Vitals after conducting extensive analysis. There are a mix of metrics we’re all familiar with, as well as a few new ones. The three Core Web Vitals are the most critical, and Google explicitly requests that site owners monitor these scores and boost them where possible.

LCP: Largest Contentful Paint

The point on the screen where the largest content element appears is measured by Largest Contentful Paint. Keep in mind that it just looks at when the most important aspect of your page loads, not how long it takes to load fully.

The LCP would be the large image if you have a basic web page with only a piece of text and a large image. It’s bound to make an impact because this is the largest piece of content to load in the browser. Your site would appear much better if you can get it to load faster. As a result, sometimes it’s just a matter of optimising the picture itself.

There used to be metrics like First Meaningful Content, which calculated the time it took for the user to see the first piece of content on the screen that was meaningful to them. Despite its name, the FMC metric had a hard time determining what was the most important thing on the computer. Data that is useless is generated by using complex metrics.

The definition of Largest Contentful Paint is simple: it is the time it takes for the largest element to appear on the screen. Photos, videos, and other forms of content may be included in these components.

What you need to know

You should start optimising for the LCP now that you know what it is. The LCP should occur within the first 2.5 seconds of the page loading, according to Google. Everything under 4 seconds needs to be improved, and everything above that is considered bad performance.

Since the first thing that loads can not be the big picture, the LCP is also dynamic. When the large image appears on the screen, the LCP switches to it.

Google provides a number of resources to assist you in locating all of these items. PageSpeed Insights, for example, provides a wealth of information on Web Vitals as well as a lot of tips on how to boost your website. When we run via PageSpeed Insights, we get many scores and recommendations. The LCP in our case was a big picture. PageSpeed Insights correctly identified the feature, as shown in the screenshot below. Now you know what you need to work on!

The LCP is influenced by a variety of factors, according to Google:

Slow server response times can be improved by optimising the server, using a CDN, caching assets, and so on.

JavaScript and CSS are rendering-blocking, so minify your CSS, defer non-critical CSS, and inline critical CSS.

Tools that take a long time to load: optimise your photos, preload resources, compress text files, and so on.

Client-side rendering issues: use server-side rendering and pre-rendering instead of vital JavaScript.

More information about LCP’s history and how to optimise for it can be found on Google.

FID: First Input Delay

The time it takes for the browser to react to the user’s first contact is measured by the First Input Delay. The page will become more sensitive the faster the browser responds. If you want to have a good experience for your users — and who doesn’t? — you should improve the usability of your sites.

When the browser is also doing other work in the background, delays occur. So, the page has loaded, and everything appears to be in order. But nothing happens when you press the button! This is a negative experience that contributes to anger. Even if the delay is minor, it will cause your site to feel slow and unresponsive.

A browser must do a great deal of work, and it might be necessary to temporarily pause such requests before returning to them later. It won’t be able to do anything at once. We’re asking a lot of browsers as we create ever more complex pages, which are mostly driven by JavaScript. We need to concentrate on the FID to speed up the process of bringing content on the screen and make it interactive.

The FID counts all interactions that occur while the page is loading. Taps, buttons, and key presses are examples of input actions; zooming and scrolling are examples of interactions. To appear sensitive, Google’s new metrics need a FID of less than 100ms. Everything between 100 and 300 milliseconds needs to be improved, and everything beyond that is considered bad performance.

What you need to know

One thing to keep in mind is that you can’t calculate the FID until the user interacts with it. This means that Google can’t simply predict the FID using data from the lab; they’ll need data from actual users, or “ground data.” This also means that this data is less controllable than lab data since it is collected from consumers using a variety of devices and in a variety of settings. This is one of the reasons why data may appear to change from time to time.

If you want to boost your grades, JavaScript is often the cause of poor results. While JavaScript allows us to create amazing interactions, it can also result in slow websites with complex code. While executing JavaScript, the browser often cannot respond to user input. You’ll instantly boost your page experience scores if you improve your JavaScript code and how it’s handled.

However, this is the most difficult part. Most websites will benefit significantly from reducing the time it takes to execute JavaScript, breaking up complex tasks, and eliminating unused JavaScript., for example, has a decent ranking, but it’s not flawless. We are also hampered by mechanisms that prevent us from achieving perfect scores. Some of these are difficult to repair, and others are needed for the proper operation of our website. Examine the results and see what you can accomplish. Find the enhancements that are the simplest to implement or that result in the most significant performance gains.

CLS: Cumulative Layout Shift

Cumulative Layout Shift is the third Core Web Vital, and it’s a brand-new one. This metric tries to figure out how ‘stable’ things load on your computer. It examines how much and by how much things bounce around when loading. You can imagine a button appearing on the screen from time to time, allowing users to press it. However, a broad content area is still being loaded in the background. What’s the end result? The button pushes down a little when the material is completely loaded, just when you want to touch it. Frustration rises once more!

Ads are prone to these layout changes. Many websites rely on advertisements for revenue, but they are often loaded in such a way that users are frustrated. Furthermore, several complex sites have so much going on that they are slow to load, and content is loaded as soon as it is available. This can also cause content or CTAs to hop around on the screen, allowing slower-loading content to take their place.

Take, for example, CNN’s website is no exception to the rule that news websites are complicated and sluggish to load. On a PageSpeed Insights test, it gets a very low score. If you look at the issues and tips further down the list, you’ll see that at the time of writing, we discovered no fewer than five moving elements. Many elements hop about while loading this page, and it takes a while for it to settle and become useful. Users aren’t always careful, so they want to press a button as soon as it appears on the screen, only to miss it when a large ad appears in its place.

What you need to know

To evaluate the movement of elements, the Cumulative Layout Shift compares frames. It measures the magnitude of layout changes by combining all of the points where they occur. Anything below 0.1 is considered fine by Google, while anything between 0.1 and 0.25 needs improvement. Anything above 0.25 is considered bad.

Of course, the score only considers sudden changes. A configuration change does not occur when a user clicks the menu button and a fold-out menu appears. However, if that button does cause a significant change in design, you should make that clear to the consumer.

Ads, as I previously said, are one of the key causes of this. They’re usually written in JavaScript and aren’t well-optimized, and they’re served from a third-party server. Every move adds to the slowness, and you’ll have to work hard to get your advertising to appear in the right place at the right time. However, there is another factor that contributes to major layout changes: photographs.

Developers don’t often define the width and height of an image in the code, instead relying on the browser to determine how the image should be shown on the screen. When viewing a page that contains both images and text, the text will appear first, followed by the images. If the developer hasn’t set aside space for these images, the top portion of the loading page will be filled with text, encouraging them to begin reading. The photos, on the other hand, load later and appear in the same place as the document. This causes the user to become irritated as the text is pushed down. As a result, always specify the width and height of CSS images to ensure that there is enough room for the images to load.

Google has a lot of information on CLS, like how to optimise for it. Google is also looking for feedback on how to boost CLS scoring.

Tools to measure Web Vitals

  • There are numerous resources available to assist you in monitoring Web Vitals and improving your site’s results. Many of them were listed in the first Page experience post I wrote a while back. You’ll find a list of them there. I’d like to highlight a few of the most critical ones here:
  • Insights into PageSpeed: With both field and lab info, PageSpeed Insights has evolved into a full-service measuring tool. Furthermore, you will receive guidance on how to change your situation.
  • Shipwreck: Lighthouse was created by Google to audit PWAs, but it’s now a fantastic tool for monitoring results. It includes multiple audits that PageSpeed Insights does not, as well as SEO checks.
  • You can now get insights from your site directly from Search Console with the Core Web Vitals study! It’s great to get a sense of how your site is doing.
  • Chrome includes a Core Web Vitals report (starting with Chrome 88) and a Core Web Vitals overlay (starting with Chrome 90), with more on the way.

These are the Core Web Vitals

Google’s algorithms will be updated in June 2021 to include a new ranking factor: page experience. Google created a new collection of metrics called Web Vitals to assess page experience. These Web Vitals include three main metrics: Largest Contentful Paint, First Input Delay, and Cumulative Layout Change. These are the three pillars of Google’s page experience update: consistency, responsiveness, and visual stability.

Continue to put the users first and build a fantastic website!

Need help with getting your business found online? Stridec is a top SEO agency in Singapore that can help you achieve your objectives with a structured and effective SEO programme that will get your more customers and sales. Contact us for a discussion now.