The Google Chrome User Experience report, or CrUX report, provides real user measurements from Chrome users that have opted-in to syncing their browser history and have usage statistic reporting enabled.
The statistics are updated daily and report a rolling 28 day average of the last 28 days.
Metrics Gathered By The Report:
First Contentful Paint: When the browser first renders any text or image (including background images)
Largest Contentful Paint: Marks the time when the page's main content has likely loaded.
First Input Delay: Measures the responsiveness of a page to user input, eg a key press or a mouse click.
Cumulative Layout Shift: Measures visual stability of a page, ie does content move as the page loads.
These metrics are defined in Google's Web Vitals
The metrics can be viewed by device type (Phone, Tablet, Desktop), connection speed, (4G, 3G, 2G) and are broken down by the proportion of visitors that match the 'good', 'needs improvement' and 'poor' guidelines. The report also shows the 75th percentile score for the website which is used to determine whether a website actually passes the recommendations.
The 75th percentile score from the CrUX report is what will be used by Google as a search signal for organic search from May 2021.
Data is available via PageSpeed Insights, Google's BigQuery project and Google Webmaster Tools. Google also have an API for querying. This API is what we use in our site speed competitor comparison report .
Unless your website is reasonably busy it won't appear in the report.