Privacy & analytics.
Mahjong Reference is designed to collect as little information as practical while still learning which parts of the site are useful.
Analytics
The site uses PostHog Cloud EU for privacy-conscious web and product analytics. It helps answer questions such as which pages are visited, how people move between pages, and which supported rules profiles people choose.
PostHog is configured in cookieless mode. Mahjong Reference does not ask PostHog to write analytics cookies, local storage or session storage. Person profiles and session replay are disabled, interaction autocapture is disabled, and the PostHog project is configured to discard client IP addresses.
Analytics can still include technical context needed to understand aggregate use, such as the page path, referrer, browser or device information, and a privacy-preserving server-generated identifier. The site does not send player names, entered hand contents or free-text game data to PostHog.
Game recovery
In-progress games and finished ledgers are kept in this browser on this device. They are separate from analytics and are not used to identify you in PostHog. Clearing site data, using private browsing, switching browser or device, or running out of browser storage can remove or prevent access. Print or save finished ledgers to keep a separate copy.
Further information
PostHog publishes information about its privacy controls and EU hosting at posthog.com/docs/product-analytics/privacy.
The analytics configuration and measurement plan are also documented in the public Mahjong Reference source repository so the implementation can be inspected.
Last updated 17 September 2026.