Privacy Policy
You can play and learn without an account. Game and course progress stay in your browser. The website uses Cloudflare traffic analytics and offers optional product usage analytics, described below. Optional analytics are off until you allow them.
Last updated: September 28, 2026. The website changes below do not add analytics to the iOS app.
The short version
- No account, email address or real-money wager is needed to use the website.
- Your game save, answers and course scores are stored locally for the features you use.
- Cloudflare Web Analytics supplies aggregate traffic and performance measurements.
- Optional usage measurement uses a random browser identifier to measure starts, completions and return visits. No advertising profiles or session recordings.
- You can turn optional analytics off or delete usage history for the current browser identifier below.
The iOS app
Blackjack Odds: 21 Trainer is entirely on-device. The odds engine, the strategy chart, the counting drills and the progress tracking all run locally, which is why the app works in aeroplane mode.
Your bankroll, drill history, mastery map, cost ledger, session records and settings are written as JSON files inside the app's own Application Support directory. That data never leaves your phone. It is not backed up to any server we control, it is not synced between devices, and we cannot see it. Deleting the app deletes all of it permanently — there is no copy anywhere else, so there is nothing for us to restore and nothing for you to request.
The app contains no analytics library, no crash-reporting service, no advertising framework and no third-party SDKs of any kind. Its App Store privacy label is Data Not Collected.
The website
The website has no login, newsletter form or checkout. The trainer stores its balance, settings, stats and mistake log under bj21-save-v1. The beginner course stores scores and an unfinished lesson under bj-beginner-course-v1. Other practice tools may store their own preferences locally. Clearing browser site data erases local progress.
Optional usage analytics
If you choose to allow usage analytics, we send a limited set of events to our own analytics endpoint, hosted by Cloudflare: page visits, first hand in a session, completion of ten coached decisions, lesson starts, lesson scores and course completion. We do not send individual answers, cards, bankrolls, names or email addresses.
Each event includes a random browser identifier, a session identifier, time, page path without query parameters, the session landing-page path, a broad referral category (such as search or social), a small/large screen category and country inferred by Cloudflare. We do not store IP addresses or full user-agent strings in our product analytics database. Cloudflare necessarily processes network information to deliver requests.
The random identifier is stored in bj-usage-browser-v1 and rotates after 90 days. The preference is stored in bj-usage-choice-v1; a tab session is stored in bj-usage-session-v1 and restarts after 30 minutes of inactivity. Identifiers distinguish browsers, not verified people. We do not track you across unrelated websites or sync identifiers across devices.
We use this information to understand whether the site helps people practice and return. Events are kept for 90 days and removed by a daily cleanup, which can take up to one additional day. Cloudflare may retain recovery copies according to its platform retention. Reports can contain aggregate counts without browser identifiers.
Consent is optional. Refusing or withdrawing it does not limit the trainer or course. We honor Global Privacy Control and Do Not Track signals by keeping optional usage analytics off. Turning analytics off stops future optional events; Delete usage history also removes stored events for the current browser identifier. If you clear site storage first, we lose the identifier needed to locate those records; they will expire under the retention schedule.
Other website requests
- Cloudflare hosting and traffic analytics. Cloudflare serves the site, processes network information for delivery and security, and provides aggregate page, referrer and performance analytics. Its Web Analytics product uses no analytics cookies or persistent visitor identifier. This aggregate service is separate from the optional product measurement above. See Cloudflare’s privacy policy.
- Google Fonts. Pages request typefaces from Google, which receives network information including an IP address. See Google’s privacy policy.
Children
This is a strategy trainer, not a gambling service — it uses play chips and takes no real money — but blackjack is casino subject matter. The site and the app are not directed at children under 13, and we do not knowingly collect personal information from children under 13.
Your choices and requests
Use the controls above to withdraw optional analytics consent or delete usage history associated with your current browser identifier. Clearing course progress and game progress are separate actions within those tools. For questions or requests concerning your information, contact spencer@blackjackoddstrainer.com. The rights available to you depend on applicable law.
Changes to this policy
If this ever changes — for instance if an account system is added — this page will be updated and the date at the top will change. We won't start collecting data quietly and describe it here afterwards.
Contact
Questions about this policy, or think we've got something wrong? Email spencer@blackjackoddstrainer.com.