Check If Your Site Passes Core Web Vitals Assessment

Karolina Szczur

Karolina Szczur

October 20, 2021

We created a free, simple tool to check if your site passes the Core Web Vitals assessment. With Core Web Vitals Checker, you can see how many site visitors have a good experience and if your site is likely to lose ranking (due to poor performance) in Google. All based on Google’s Chrome User Experience Report (CrUX) data.

What are Core Web Vitals?

Core Web Vitals is a set of metrics portraying three aspects of user experience: loading (Largest Contentful Paint), interactivity (First Input Delay) and visual stability (Cumulative Layout Shift). With Core Web Vitals, you can quantify and improve user experience across your websites and applications. It’s a critical set of metrics to track.

Core Web Vitals are a modern way of understanding how people experience your web properties. They are also essential signals for Google ranking. In short, the worse your Core Web Vitals, the more your ranking will be impacted.

Check your Core Web Vitals

Core Web Vitals Checker generates a simple, shareable report for a page or entire domain (set of pages, also referred to as the “origin summary”), highlighting Largest Contentful Paint, Cumulative Layout Shift, First Input Delay and First Contentful Paint. The first three metrics form Core Web Vitals, while First Contentful Paint is deemed a Web Vital—another essential metric worth tracking.

Core Web Vitals report for calibreapp.com domain
Core Web Vitals report for calibreapp.com domain.

With Core Web Vitals Checker, you can see if your website passes or fails Google assessment guidelines. You can also analyse the percentage of good and poor user experiences for each metric and determine where you should make improvements.

We built it as an accessible starting point for checking speed and sharing with your team (or the world!). Each report has its unique URL and generated share card, so you can tweet it, send it to Slack, email it or use any other medium that suits you:

Preview of the generated shared card with your results
Preview of the generated shared card with your results.

We think about Core Web Vitals Checker as a traffic light system—a tool that can help anyone, no matter their knowledge and expertise in web performance, find out about crucial user experience aspects.

You can see how your metrics change for different devices, such as Desktop, Tablet and Phone and the share of visitors with good, to improve and poor experiences. Intentionally, it doesn’t provide advanced filtering or data visualisation, but it’s a starting point for further investigation.

Where does the Core Web Vitals data come from?

Your report is generated based on Google’s Chrome User Experience Report (CrUX) API—a public dataset of real user experiences for millions of websites. CrUX collects data only for Chrome browser users (also excluding devices with the iOS operating system). It’s important to remember that while CrUX is a substantial data set, it still excludes specific demographics, such as:

The dataset is updated daily and aggregates the previous 28 days of data.

Why is there no or partial data for my site?

Some sites might not have enough traffic to be included in the CrUX report. New sites are added to the dataset every day, so keep checking in the future or run a report on the entire domain instead of a specific page. If your report isn’t there yet, you can also start monitoring Core Web Vitals in Calibre!

The Core Web Vitals assessment also treats First Input Delay as an optional metric. Lack of First Input Delay measurement means there is no user input for a given page visit. Without FID, your review is calculated based on the remaining Core Web Vitals: Largest Contentful Paint and Cumulative Layout Shift.

How to improve Core Web Vitals?

There are numerous ways to improve Core Web Vitals. The best way to start is to find out where your metrics are at and continuously monitor page speed to get a better picture. Tools like Calibre can help you visualise speed, give targeted advice and alert about page speed goals.

If you don’t know where to start, head to our getting started guide! We also have a handy article about improving one of the Core Web Vitals, Cumulative Layout Shift and an overview of all Core Web Vitals. If you’re beginning your journey at page speed, you might also want to know how to convince your boss or plan and deliver on speed.

We hope that with Core Web Vitals Checker helps you understand and share information about critical metrics!

Karolina Szczur

Karolina Szczur

Karolina is the Product Design Lead at Calibre. With years of design experience under her belt, she’s responsible for the comprehensive user experience spanning over product, visuals and content. Find her on Twitter or LinkedIn.

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Addy Osmani

Addy Osmani

Engineering Manager at Google Chrome