Note that this feature is in a private beta program now, related to a renewal of the Full Page Check monitor. See the knowledge base article Full Page Check - What’s new (beta program) for more information on the new features of this monitor type.
Based on an initiative by Google to simplify the conversation about website optimization, Core Web Vitals are a set of key metrics to measure website performance. These metrics reflect different aspects of the user experience when visiting any site, such as loading speed and visual stability. Poor scores on such metrics may directly affect your search engine rankings, meaning it’s important to keep track of these key numbers, so you can ensure your page is and remains properly optimized.
Uptrends' Full Page Check (FPC) monitor type comes with the option to display the set of Core Web Vitals (plus some additional information). This article will provide you with an overview of the metrics shown and what they mean exactly.
Uptrends displays the following Core Web Vitals (and related metrics):
- First contentful paint (FCP): The FCP measures how long it took the browser to render the first content on the page.
- Largest contentful paint (LCP): The LCP measures the time between the FCP and when the largest single element (image or text block) was rendered on the page. It marks the point in the page load timeline when the page’s main content has loaded.
- Time to interactive (TTI): The TTI is an indication of the time between the start of loading, and when the page can reliably respond to user inputs. As such, it’s a good way to measure how long the user actually ends up waiting for the page to load. It’s necessary to determine the TTI in order to calculate the Total blocking time.
- Total blocking time (TBT): The TBT is the time between the First contentful paint and the Time to interactive. It reflects the time the page spends loading and is visible to the user, but cannot yet be interacted with (hence, ‘blocking’).
- Cumulative layout shift (CLS): The CLS is the last metric determined, after the page has finished loading completely. It describes the measure in which the page layout shifts (visible elements moving from one place to another) after the page has become interactable, indicating its visual stability.