What are core web vitals?

Posted by: Josh Millard

You may or may not be aware that the way in which your webpages are now ranked on Google is based to a larger extent on user experience. User experience has always been hugely important in the development of the best websites, offering the opportunity for the highest search engine ranking, but this importance has now been enhanced.  The introduction of Core Web Vitals is something that should be embraced by everyone as it drives greater user experience on your website as well as offering greater ranking opportunities as part of a customer centric design and development upgrade.

So what are Core Web Vitals?

Firstly, it is important to note that the Core Web Vitals that have been identified by Google are just part of a larger network of ranking factors and are not to be addressed in isolation. The metrics that were important before are still as important but you must know take into account the greater emphasis Google is placing on user experience. With that being said, we can introduce:

  • LCP: Largest Contentful Paint
  • FID: First Input Delay
  • CLS: Cumulative Layout Shift

When converted from technical references these are:

  • Loading performance (how fast do things appear on the screen?)
  • Responsiveness (how fast does the page respond to user input?)
  • Visual stability (do things move around on the screen whilst loading?)

These are to be a focal point for Google over the coming years in an attempt to drive higher quality user experience across the world. These measures may be adapted or enhanced as time progresses, but these vitals are of huge importance right now.

How are they measured?

To understand the levels of improvement each webpage requires, Google has provided a scale to score the performance of each page against each of the three core vitas identified: 

  • Loading performance (how fast do things appear on the screen?)
  • 0 – 2.5 seconds – good
  • 2.51 – 4.0 seconds – need improvement
  • 4.01 seconds + – Poor


Responsiveness (how fast does the page respond to user input?)

  • 0 – 100ms – Good
  • 101ms – 300ms – Needs improvement
  • 301ms + – Poor


Visual stability (do things move around on the screen whilst loading?)

  • 0 – 0.1 – Good
  • 0.11 – 0.25 – Needs Improvement
  • 0.26 + – Poor


To better understand the expectations of Google and the work required to meet the, lets look at each of the Core Web Vitals individually.

LCP: Largest Contentful Paint / Loading performance

Largest Contentful Paint measures the time it takes for the largest element of any given page to appear on the screen in complete form. This may be an image, a video or a design element that is specific to an individual page or further types of content. If the largest element of your page loads quickly (under 2.5 seconds) then Google will score the page well and will add this to the other page metrics. If it loads slowly (over 4 seconds) then the page will score poorly which can have a negative effect on ranking positioning.  Optimising the largest content element on your page can quickly improve the loading performance but, like everything, content is unique to all of us so must be reviewed individually to identify the best action to take in achievement a strong Core Web Vital measurement.

FID: First Input Delay / Responsiveness

The First Input Delay measures the time it takes for a page to respond to a user’s first interaction. If a page is poorly optimised, has huge content elements to load or has been poorly developed, the browser will still be working on multiple tasks when a user is attempting to interact. This results in delays, and the consequences will be a poor measurement against Googles Core Web Vitals scoring but just as importantly, as poor user experience. The FID measures all interactions that happen whilst the page is loading including taps, clicks, and key presses. As you are well aware, the world is only getting faster, if users cannot access the information they want, when they want, they will move on quicker than it takes your page to finish loading!

CLS: Cumulative Layout Shift / Visual Stability

The third Core Web Vital is a Cumulative Layout Shift. This metric ascertains how stable the content of a page is and remains to be. Often, full page content loads at differing times which can lead to the movement of images and text from their original positions. Users are often reading information when it suddenly moves or attempt to click on an option when it disappears, frustration grows, time on site declines. On most occasions these are development errors which leads to your browser making decisions on image size and content positioning. Design and development quality are imperative in the delivery of high-quality user experience and that is why this new metric has been given greater importance. This, like all other vitals, should not be seen as an inconvenience but as an opportunity to offer your customers the highest quality and best experience possible when visiting your website. You have less than second to convince visitors to stay on your sight, improve your odds.

Google Web Vitals are so called because the metrics used are of vital importance to the performance of webpages and the subsequent experience of users. Core Web Vitals are a new metric added to the spiderweb of review functions that are performed continually to assess the quality of your website and its content. The performance measures are changing so quickly it is extremely difficult to ensure you react as quickly as is needed and improve all of your webpages to reflect the quality required. That is why Penn Studio does it all for you, consistent research and application of the changing needs of Web Vitals has allowed Penn Studio to offer businesses their expertise. As part of a growing range of support services Penn Studio can offer improvements across your existing website or work alongside you to develop a new site that meets all of the quality criteria that search engines and your customers require.