Cookies and storage

Essential account session

Signing in retains a session token in browser local storage under an authentication-service key. Signing out removes the app session. The first lesson of each section is readable without an account; account progress is kept in the backend database, never in guest browser progress storage. Old browser progress is ignored.

Theme preference

The key sysdepth.theme remembers your light or dark choice. It contains no learner progress. The theme control changes it; clearing this site's storage also removes it, but signs you out.

Your external-content choices

YouTube remains unloaded unless you choose Load YouTube video. Choosing not to load it is equally available: keep reading. Unload YouTube video removes the current player. The choice is per player, not a remembered blanket consent; unloading does not delete YouTube's storage or undo prior requests.

Run or Check downloads Pyodide 314.0.7 from jsDelivr for browser Python. Do not run it if you do not want that external request; code and worked examples remain readable. Stop discards the active isolated runner. The CDN/runtime download may remain in normal browser cache. Browser models drawn on lesson pages need no external runtime and save no state.

Fonts, cookies and diagnostics

Device fonts are used without external font requests. The application code installs no analytics or advertising cookie. The hosting platform measures aggregate visits to the published site (sources, pages, countries, devices) without linking them to accounts; its exact mechanism, storage and retention have not been independently verified. Hosting infrastructure and the editor preview can behave differently; we have not independently verified production hosting cookies or diagnostic retention.

Server logs and host-provided error hooks may receive errors, stacks and page paths. There is no invented Accept all banner: the application adds no optional tracking. If an additional analytics tool is introduced later, it must be blocked until a clear choice with reject and revoke controls.

See the privacy notice and terms. For product questions use Feedback.