"Privacy-first analytics" is one of those phrases that means something different depending on who's saying it. Some tools use it to mean "we don't sell your data to advertisers (yet)." Some use it to mean "we set fewer cookies than the competition." Both are weak definitions.
A useful definition is architectural rather than promissory: the tool is built so that it cannot identify a person, cannot follow a person across sites, and cannot reconstruct a session beyond what is strictly necessary to count a page view. That property is enforced by the code, not by a privacy policy.
What that looks like in practice
For WebmasterID, that means: no third-party cookies, no localStorage tracking, no fingerprinting (canvas, audio, fonts, device entropy), no cross-site identifier, and no session replay. What is collected is the small set of fields that actually answer analytics questions: site_id, URL, pathname, referrer, UTM parameters, language, screen width, event name, timestamp.
IP addresses are anonymised at the ingestion edge — IPv4 last octet zeroed, IPv6 truncated to /48 — and the raw form is never written to the database. The full breakdown lives at /privacy-first-analytics.
Why the transport layer matters
The browser tracker submits events as a plain string body via navigator.sendBeacon. The browser attaches Content-Type: text/plain;charset=UTF-8 — a CORS-safelisted MIME — so no preflight is required. This sounds like a tiny implementation detail, but it has real privacy consequences: credentialed CORS preflight effectively asks the server to opt in to credentials. Avoiding the preflight removes that surface entirely.
Honest limits
Privacy-first analytics is not magic. There is still an HTTP request, the request still has an IP source address, and the ingestion server still has to make a decision about what to log. What "privacy-first" means is that the product is engineered so those decisions are conservative by default and the resulting stored data is not enough to reconstruct an individual.
For a complete view of how that plays out in the product, see /architecture. For why we made these choices, see /philosophy.