New Google Criteria: Core Web Vitals 
Marketing & Advertising

New Google Criteria: Core Web Vitals 


In SEO marketing, companies, blogs, websites, and online platforms compete daily. The top of Google’s list is where they want to be.

Of the countless listings on Google, 90% of listed sites never make it to the front page. The 10% that do are the paid adverts, knowledge graphs, and approximately ten organic listings. Traffic among them is uneven. Less than 3% of web users make it to results on the follow-up pages. 

Up to this point, the main influencing SEO marketing mechanisms have been headings, content, title tags, keywords, image descriptions, internal links, backlinks, etc. With a focus on quality control, the mammoth engine, Google will be factoring in a new requisite. 

Core Web Vitals are to become a determining component of technical SEO agencies in the UK. It can also be expected to and is prone to redefine search results. While traditional SEO marketing essentially embraces relevance, distance, and prominence Core Web Vitals will entrench value. 

What Are Core Web Vitals?

Core Web Vitals are a separate set of metrics determining the user experience (UX) on websites. The latter incorporates three different page-speed and client node interaction measurements. The cumulation of these factors will feature in a scoring system that determines the priority a page receives as a listing.

The Three Elements of Core Web Vitals

Largest Contentful Paint

Largest Contentful Paint (LCP) is a measurement created by Google to ensure user satisfaction. This parameter focuses more on performance rather than presentation. If the page takes too long to load and the web surfer leaves, this is deemed unsatisfactory.

The loading time of the webpage and Google experience factors like image tags and video thumbnails determines the LCP rating. Background images with CSS and text elements such as paragraphs, headings, and lists also get monitored for fluency.

Causes of Poor LCP

Slow Server Response Times

The rendering speed of a website is dependent on the reaction time of a server. The slower the server is, the longer it will take anything to display on the screen of a device.

The primary solution here is to optimise your server.  Caching assets and serving HTMLs cache-first expedites service processes. Additionally, it is advisable to route users to a nearby CDN. By establishing third-party connections early, latency becomes minimal, which is important for mobile responsive websites. 

CSS and JavaScript render-blocking.

Browsers deliver content by parsing HTML markups into a DOM tree. Should the parser come across any external style sheets, it pauses. Scripts and external style sheets delay the distribution of blocking resources, FCP, and ultimately LCP.

CSS and Java are robust and can lose a “lot of weight” through deference, minimisation, and minification. Software available for Java compaction include UglifyJS2, Closure Compiler, and YUI Compressor. CSSnano, UNCSS, and CSSO are all mechanisms capable of compressing CSS. The time of loading optimisation will improve with the deployment of these tools. 

Poor Resource Load Times

While the increase of CSS and JavaScript activity produces bad results, other components prove just as problematic. Elements negatively affecting LCP are < image >, < img > and < video > and block-level components containing text nodes.

The optimisation and compression of image and text files will help here. By preloading necessary resources and caching assets, while using a different service worker, the time needed, reduces.

User End Rendering

Sites that do most of their rendering on the client end forfeit a fair amount of control. The disadvantage of this option becomes apparent with the use of large JavaScript bundles. In most cases, the content does not display until JavaScript completes its rendering; it will jeopardise the LCP ratings. 

JavaScript minimisation is crucial, and server-end rendering is preferable over user-end. Another solution is pre-rendering which will assist with the time of loading optimisation.

First Input Delay

First Input Delay (FID) measures the time from the initial user interaction to when the browser responds. It is a crucial factor in whether the client will leave the site or not. Delays generally occur when a browsers’ main thread is busy. 

JavaScript files loaded by local apps usually are to blame for FID issues. What happens is browsers attempt parsing and execution, but latency occurs, leading to unresponsiveness on end devices. A low FID rating may ascertain that the site or page in question is unusable. 

Causes of Poor FID


Generally, while the main thread is busy, the browser can’t respond to interactions. Heavy JavaScript execution compounds this problem imposing delays on loading speed.                               

By breaking up long tasks, you can alleviate the backlog. Additionally, limiting JavaScript runtime should improve responsiveness. The use of a web worker is also helpful. These are all ways of optimising the website metrics for interaction.

Cumulative Layout Shift

The Cumulative Layout Shift (CLS) metric measures the stability of a web pages’ design. It functions to ensure that client interactions flow as naturally as possible. Web surfers often experience interruptions or jumps while viewing content on a site. Hence, it leads to a break in concentration and creates a poor experience. 

The inconvenience is a result of weak design. The effects prevail on mobile responsive websites and desktop browsers.

The lack of correct design elements instigates visual instability. The latter tends to force sudden layout shifts, many a time causing the user to click on undesired content inadvertently. Typical examples are sites with pop-up ads. 

New designs, even though correctly structured, may also slow down web pages. The Google algorithm compensates by allowing a 500ms omission before it begins its calculation process.

Common Causes of CLS

Images Without Dimensions

The exclusion of width and height size attributes for both video and imagery will result in a low ranking. Many people don’t reserve space for media, and this results in jumps and shifts. 

The solution here is simple; always include width and height. The other option is CSS aspect ratio boxes. They’re handy for the reservation of space on websites. It’s especially useful on sites that host ads.

Ads, Embeds, and Iframes Without Dimensions

Adverts are large contributors to the issue. Ad networks opt for dynamic sizing as opposed to the static variant, which increases traffic to websites. Unfortunately, this is at the expense of the desktop or mobile experience. 

Certain widgets allow the embedding of items like videos, maps, and social media content into the webpage. The problem here is the site often has no idea of the exact size or composition of the embed. By not reserving space, instability becomes apparent once the page loads.

Pre-calculation of the necessary spatial needs for an embed or a fallback the site averts the peril of CLS. Browser developer tools are handy for obtaining the height and width for the result. After establishing this, the iframe will automatically fit the reserved space every time the page loads.

Dynamically Injected Content

Newly inserted items over old media are also what creates layout shifts. Typical examples of these are call-to-action banners. Not only do they block interaction, but they irritate rather than convince.

Once again, reserve space. Additionally, site designers can add a UI skeleton. The latter is a placeholder that will prevent the text from migrating when the image loads.

Web Fonts Causing FOIT/FOUT

Downloading and rendering web typefaces are instrumental to a Flash of Unstyled Text (FOUT). In this case, a new style replaces fallback print. 

An additional consequence is Flash of Invisible Text (FOIT) which hides the typeface until a new case becomes available. 

Font Loading API reduces the time needed to get the necessary lettering styles, thus minimising or eradicating the occurrence of FOUT and FOIT.

Core Web Vital Metrics

As noted, the three Core Web Vital elements have individual measurements. Each one graded according to different time standards.

  • A good LCP rating is less than 2.5s. Google will grant leniency for anything under 4s, but this still means that there is room for improvement.
  • The unit of measurement of FID is milliseconds and if the time between user input and webpage reaction falls anywhere under 100 this is ideal. A metric of 300ms is acceptable, but it hints at problems to come. Anything above 300ms leads to the relegation of the web listing.
  • The ideal reading for CLS is zero. Google algorithms will accept 0.1, but since the maximum acceptability is 0.25, it creates too small a margin for flexibility. The website administrators may as well strive for complete perfection.

Core Web Vitals Analysis Tools

  • Web Vitals For Chrome is like any other extension, and some might not be comfortable with this option because of privacy concerns.
  • Page speed insight is a simple interface allowing you to toggle between desktop and mobile options. PC and smart device results differ irrespective of the analysis software you use. The aforementioned produces field data of real Google users over 28 days.
  • Chrome Dev Tools and Lighthouse’s designs allow them to monitor LCP and CLS. Unfortunately, the same software isn’t able to measure FID, but for that, there is TBT.

As Core Web Vitals proliferate, more monitoring tools are bound to come onto the scene.

Why is Core Web Vitals Optimization Important

The Google core update is scheduled to occur in May 2021. This means from then onwards, the usual SEO signals won’t be sufficient to maintain a high ranking on Google. 

It’s an implementation of a standard advocating quality UX. The sites abreast with the new criteria won’t be affected. Web pages that haven’t adjusted are sure to feel the effects, despite how effective their SEO is. Listings with weak Core Web Vitals will drop in ranking, making room for entities who are compliant. 


By setting a new regulation in SEO marketing, Google paves the way for improvement. The Core Web Vital standard is the first, and many more are sure to follow. These measures create a platform for a new era of the internet to merge with other flawlessly emerging technologies. Additionally, you can use these tips to increase your website loading speed.


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