Privacy Policy
Last updated:
Sudoku a Day is operated by Ocho B.V. This policy explains what we collect, why we use it, and the choices you have. We do not sell personal data.
What we collect
- Game and account data: puzzle progress, scores, leaderboard entries, profile details you choose to provide, and the technical identifiers needed to keep that data synchronized.
- Basic usage data: limited technical and aggregate usage information used to keep the site reliable and understand general product use.
- Optional Sudoku emails: your email address, chosen language, daily or weekly schedule, IANA time zone, local delivery hour, difficulty, paper size, consent version, confirmation and unsubscribe history, and delivery outcomes such as a bounce or spam complaint.
- Delivery records: the recipient, message content, preferences, management links, and exact printable file used for an attempted email. Keeping this snapshot lets a retry use the same message and file. A separate record of the subscription, schedule, and puzzle period prevents duplicate delivery.
- Abuse prevention: short-lived, one-way identifiers derived from an email address or IP address for rate limiting. We do not store the full IP address in the subscriber database.
How we use the data
- Provide the puzzle, profile, score, and leaderboard features you use.
- Generate and deliver the Sudoku schedule you explicitly confirmed.
- Remember and apply email preferences and unsubscribe requests.
- Prevent duplicate mail, abuse, hard-bounce retries, and mail after a complaint.
- Secure, debug, and improve the service.
Recurring Sudoku email is based on your consent. Downloading a PDF does not require consent to email, and an address is not activated until its owner confirms the request. You can withdraw consent at any time using the prominent unsubscribe link in every recurring email.
Your email language is a separate preference from your time zone and delivery schedule. Changing language does not create a new subscription or renew consent. A short-lived cookie remembers the language of confirmation and unsubscribe result pages for up to ten minutes.
Services that process data for us
Cloudflare hosts the website, subscriber database, generated PDFs, queues, bot protection, and scheduled jobs. Amazon Web Services Simple Email Service delivers email and reports delivery, bounce, and complaint events. Other service providers used by the game may process only the data needed to provide their part of the service. We remain responsible for how the data is used and do not permit providers to use subscriber addresses for their own marketing.
We use OpenAI to prepare translations of our public website, email templates, and printable text. Translation requests contain that source copy and its page context. Subscriber addresses, private account information, and personal management links are not included in those translation requests.
Email tracking
Sudoku emails do not contain advertising trackers. We do not enable open or click tracking. We record operational delivery events needed to know whether a message was delivered, bounced, rejected, or reported as spam.
Retention
- Unconfirmed email requests are removed after seven days.
- Rate-limit records are removed after they expire, normally within 24 hours.
- Raw email-provider event details are removed after 30 days.
- Completed operational delivery records, including their message snapshots, are removed after 90 days without an update. An unresolved delivery can remain while it is being handled.
- A minimal record of delivered or attempted puzzle periods is retained with the subscription to prevent duplicate mail after older operational records have been removed.
- Consent evidence is kept while a subscription is active and for a limited period afterward when needed to demonstrate that mail was requested.
- A minimal unsubscribe, hard-bounce, or complaint suppression may be kept so that we do not accidentally start sending again.
Your choices and rights
Every recurring email lets you change the schedule or stop all Sudoku emails without an account, password, survey, or hidden extra step. You may also ask us to access, correct, export, or delete personal data where applicable. A suppression needed to honor an unsubscribe or complaint may be retained in minimal form.
Contact
For privacy questions or requests, email hi@ocho.so.