What is the Chrome UX Report?

The Chrome UX Report is a publicly available data source from by Google that provides information about the user experience (UX) of websites. It is based on anonymized usage data from users using the Chrome browser and includes metrics that measure important aspects of web performance and user experience. The data in the Chrome UX Report is generated from so-called "field data," meaning it comes from actual user interactions as they visit websites. As a result, the report provides a realistic insight into the performance and behavior of websites under real-world conditions.

Difference between CrUX and laboratory data:
Laboratory data is generated through simulated tests in controlled environments, e.g. using tools such as Webpagetest, Lighthouse or PageSpeed Insights. These tests mimic a user's behavior, but they are not identical to actual user experiences.

The CrUX data, on the other hand, covers a large number of users worldwide and therefore offers a broad perspective on website performance. Because CrUX data is based on real user experiences, it provides more representative results of how websites perform in the real world.

What values are included in the Chrome UX Report?

There are currently six metrics that are taken into account:

1. Time To First Byte (TTFB):
   Describes the time that elapses until the web server sends back the first bytes of data as a response after receiving an HTTP request.
2. First Contentful Paint (FCP):
   This is the time it takes for the first content to be rendered on a web page. A fast FCP value indicates that the web page loads quickly and visual content is available to the user quickly.
3. Largest Contentful Paint (LCP):
   This metric measures the load time of the largest visible content on a web page. A fast LCP value is important to ensure that important content is quickly available to the user.
4. Interaction To Next Paint (INP):
   It describes the time that elapses until the next visual update or "paint" after a user interaction (e.g. clicking on a link or button). " appears on the screen.
5. First Input Delay (FID):
   FID measures the responsiveness of a website by measuring the time that elapses between a user's first attempt at interaction and the website's actual response. A low FID value is crucial for a good user experience, especially on interactive pages.
6. Cumulative Layout Shift (CLS):
   This metric measures the visual stability of a web page by tracking how much the elements on a page move while loading. A low CLS score indicates that the page does not move unexpectedly, resulting in a better user experience.