a little clarity about your data.

you can use every lesson without an account or email address.

optional analytics

if you allow analytics, we use PostHog to measure page visits, lesson reading progress, time spent with lessons, interactive use, sharing, search result counts, performance, and error types. this helps us understand what people find useful and fix problems.

PostHog stores a randomly generated browser identifier and session information in your browser’s local storage. it lets us measure returning visits and journeys between lessons. it is not linked to an account or email address.

we do not record sessions, capture the text you type, or send calculator inputs, search terms, full referrer URLs, or error messages. page URLs have query strings removed; simple campaign labels may be included to understand where visits came from.

analytics requests go to PostHog and include connection information such as your IP address. read PostHog’s privacy notice for information about their processing.

analytics starts only after you allow it. you can turn it off below at any time; doing so stops new events and clears the analytics identifier from this browser. it does not delete events already received. do not track and global privacy control signals keep analytics off.

your preference and hosting

we save your analytics choice locally so we can remember it. your hosting connection may also generate operational logs used to deliver and protect the site, independently of optional analytics.