What information does this tool provide?
This tool provides a visual representation of the Core Web Vitals for a given url for the last 6 months (if available).
Where does the data come from?
The data is fetched from Google's CrUX API (specifically
this API). This is the same data that Google exposes via
pagespeed.web.dev or Google's search console. The tool itself does not capture or store any data.
How is this information different from that available via Google PageSpeed?
Google PageSpeed displays the current Core Web Vitals. In contrast, this tool displays the Core Web Vitals for the last six months. The historical data allows us to identify when a certain degradation or improvement happened. This enables us to correlate any performance regression to the code, infra or other changes on our website.
How does Google collect this data?
For every Url visit via Google's Chrome, the browser sends anonymized core web vitals stats to Google. Google aggregates this data and makes it available via Google's CrUX. So, the data rendered by this tool is based on real users visiting the provided Url.
Why isn't there any data for some urls?
For the urls with a low number of hits, Google doesn't aggregate and provide the stats it collects. As a result, Google doesn't make these available via Google's CrUX API.