How we compute your field CWV p75

Your Core Web Vitals field numbers come from our own beacon (~4 KB of JavaScript) embedded on your site. Every measured page navigation reports LCP, INP, CLS, TTFB and FCP via `navigator.sendBeacon` on hidden / unload.

We do not use CrUX. CrUX is a public rollup, capped at page-URL granularity and only covers pages with 'enough' Chrome traffic. Your own beacon covers 100 % of your traffic, including logged-in and low-volume URLs.

Aggregation

Raw events land in ClickHouse and roll up into an AggregatingMergeTree materialized view keyed by (workspace, project, URL, device, geo, day). p75 is computed as a merged T-Digest across the last 28 days of that view.

Sample size is the total event count included in each cohort. Small cohorts (<250 samples) are excluded from regression alerts to avoid noise.

Sampling

The default beacon sample rate is 20 % — configurable per project. Sampling gate runs client-side so unsampled pages never hit our ingest.