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Browser storage on this device
Local storage keeps the features you choose to use working across visits. Game data is not uploaded to the server.
| Key | Purpose | Duration |
|---|---|---|
| spo:v1:game:/… | Current puzzle, notes, timer, mistakes and undo history. | Until site data is cleared |
| spo:v1:daily:YYYY-MM-DD | Progress on the selected daily puzzle. | Until site data is cleared |
| spo:v1:completed | Finished puzzles and local completion records. | Until site data is cleared |
| spo:v1:settings | Auto-check and sound preferences. | Until site data is cleared |
| spo:v1:solver | Starting clues typed into the Sudoku solver. | Until site data is cleared |
Contact form session cookie
When contact delivery is enabled and you open the form, __Secure-spo_contact identifies a necessary form session. It is restricted to /contact/, sent only over HTTPS, unavailable to JavaScript and uses SameSite=Strict. It expires at the end of the browser session. The anti-forgery token expires after 30 minutes. The cookie does not track visits or store your message.
Spam protection
When delivery is configured, the form limits submission attempts using an HMAC of the requesting IP address and a timestamp in a private server database. These records contain no message text or email address and expire after 24 hours. The server also keeps access logs as described in the privacy policy.
No optional tracking
There are no analytics, advertising pixels or third-party tracking services to accept or reject. No consent banner is needed for services that are not used. Historical optional-service preferences from an earlier interface are removed from local storage when the site loads; they never enabled tracking.
Clearing stored data
You can remove local storage and cookies through your browser’s site-data settings. Clearing local storage removes saved games, settings and completion records. Blocking storage does not prevent reading the guides or playing a new game, but progress cannot be saved. Blocking the contact session cookie prevents secure form submission.
Questions
See the privacy policy for server logs and message handling, or check the contact page for message delivery availability.