Delta12 · legal
Privacy policy
In short
- Raw Apple Health data (individual heart-rate, sleep, step and workout samples) stays on your phone. Only daily summaries go to the server.
- Photos are encrypted on your phone. Only you hold the key (iCloud Keychain); we cannot open them.
- The AI only gets summaries, goals and your profile without name or e-mail. Never photos or raw Health data.
- App data is stored in the EU (Frankfurt).
- No ads, no selling of data, no analytics, no tracking.
- You can download or delete all your data in the app (Export everything, Delete everything).
- Who is the controller
- What data we process and why
- Apple Health
- Photos
- AI processing
- Purchases
- The delta12.app website
- Who we share data with
- Transfers outside the EU
- How long we keep data
- Security
- Your rights
- Consents: full text
- Delta12 is not a medical device
- Changes to this policy
1. Who is the controller
The controller of personal data in the Delta12 app and on the delta12.app website is Peter Buchlák, company ID (IČO) 87549301, Na Zlaté stoce 1886/5A, 370 05 České Budějovice, Czech Republic.
Contact for anything related to data protection: hello@delta12.app.
2. What data we process and why
| Data | Purpose | Legal basis |
|---|---|---|
| Account | Sign in with Apple. The app does not ask Apple for your name or e-mail; we receive an account identifier that your data belongs to. | Performance of a contract (Art. 6(1)(b) GDPR) |
| Onboarding profile | Goals and a note on them, year of birth, sex (optional), height, activity level, how you feel, sports, training days and time, locations and equipment, diet preferences, reminder settings, language. Used to build and adjust your plan. | Performance of a contract |
| Health data | Weight, maximum heart rate, limitations for the plan (areas and a note; not a diagnosis), daily summaries from Health, circumferences, weekly questionnaire (energy, mood, stress, sleep quality, appetite, muscle soreness, note), performance tests, the week-0 habit diary (bedtime, screens, alcohol, caffeine), baseline and plan completion. Used to build and evaluate your plan and for the weekly report. | Explicit consent (Art. 9(2)(a) and Art. 6(1)(a) GDPR) |
| Check-in photos | Comparing your progress over time. Stored on the server only in encrypted form, see Photos. | Explicit consent |
| Plan and reports | The plan, its revisions (who changed it and why), weekly and final reports, generation status and a technical record of each AI call (model and token count). | Performance of a contract; explicit consent for the AI-generated parts |
| Purchases | Verifying and redeeming a programme purchase, see Purchases. | Performance of a contract |
| Consent records | Consent type, granted or revoked, text version and time, so we can demonstrate what you agreed to. | Legal obligation (Art. 7(1) and Art. 6(1)(c) GDPR) |
| Technical records | Server providers log technical data with each request (such as IP address and time). Used for operation and security. | Legitimate interest (Art. 6(1)(f) GDPR) |
You can edit your profile, health data and plan in the app at any time under Profile. Reminders are scheduled on your phone; we do not send push notifications from a server.
3. Apple Health
With your consent, Delta12 reads sleep, resting heart rate, HRV, steps, daylight, active minutes, weight and workouts from Health on your phone. The raw samples never leave your phone. Only daily summaries (for example sleep duration or average resting heart rate for a day) go to the server, together with their source: device, app and, for HRV, the measurement type. Workouts from Health are matched with your plan on the phone so you don't have to tick them off.
We do not use Health data for advertising and we do not sell it. Delta12 writes nothing to Health. At your request, the app can send runs and rides from your approved plan to the Workout app on Apple Watch; this happens only between your own Apple devices.
You can turn off Health access at any time in iOS Settings. What happens when you revoke consent is described in the full consent text.
4. Photos
Check-in photos can only be taken with the in-app camera. Each photo and thumbnail is encrypted on your phone with its own random key (AES-GCM), which is in turn encrypted with your master key stored in iCloud Keychain. Only the encrypted file and metadata go to the server: time, pose, check-in, a file fingerprint (SHA-256) and an Apple App Attest signature confirming the photo was taken in the app.
Without your key nobody can open the photos, not even us. In Profile you can save a recovery key in case you lose access to iCloud. If you lose both iCloud Keychain and the recovery key, the photos cannot be recovered. Photo comparisons, the result card and the time-lapse are all created on your phone.
5. AI processing
Your plan, next-week proposals and weekly report summaries are written by a language model from Anthropic. The app never talks to it directly: requests go through our server (Supabase Edge Functions), which also holds the AI key.
We send the AI: goals, limitations for the plan and your profile (without name or e-mail), metric summaries (averages, baseline, weekly trends), check-in values, test results and plan completion.
We never send: photos or raw Health data.
Anthropic processes this data as our processor under a data processing agreement. AI output is always a proposal: the AI never changes your approved plan on its own, you approve every change. There is therefore no automated decision-making with legal or similarly significant effects within the meaning of Art. 22 GDPR.
If you revoke consent to AI processing, the AI stops building your plan, proposals and report summaries. Your approved plan stays and you can keep adjusting it yourself.
6. Purchases
The programme is bought in the app through the App Store. Apple is the seller: Apple handles payment, payment details, taxes and refunds, and we never see your card details.
To verify the purchase and unlock your programme, we store a purchase record with your account: product, transaction identifiers, date, environment (production or test), price and currency when Apple provides them, and Apple's signed transaction as proof of purchase. The record is included in your export and is deleted when you delete your account.
What remains after you delete your account: only the Apple transaction ID and the time it was redeemed, with no link to you, your account or your programme. Without it, one paid purchase could be redeemed again and again (delete the account, sign in again, restore the purchase). The transaction ID alone does not identify you without Apple's receipt, which only you have. Legal basis: legitimate interest in preventing abuse (Art. 6(1)(f) GDPR).
7. The delta12.app website
The website uses no cookies, analytics or tracking code. Fonts are served from delta12.app itself; no request goes to Google.
Waitlist: when you fill in the form on the website, we store your e-mail, whether you are an individual or a coach, optionally your main goal, number of clients and how you heard about us, the page language and the time. The data is stored in the EU (Frankfurt), used only to contact you about the start or an interview, and read by nobody but the controller. The legal basis is your consent, given by submitting the form; we delete the list once the app launches, or earlier on request by e-mail.
8. Who we share data with
We do not sell data and do not use it for advertising. Only these providers work with it:
- Supabase (processor): database, sign-in, storage of encrypted photos and server functions. The project runs in the EU region, Frankfurt (eu-central-1).
- Anthropic (processor): the language model for plans and reports, only to the extent described in section 5.
- Apple: Sign in with Apple, the App Store (sale and payment), iCloud Keychain (photo key), App Attest and Apple Health. For its own services Apple is an independent controller under its own privacy policy.
- Vercel (processor): hosting of the delta12.app website. The app sends no data through Vercel.
No coach or other user can see your data. If sharing with a coach is added in the future, it will only happen with your explicit permission.
9. Transfers outside the EU
App data is stored in the EU. Data sent to the AI (Anthropic) and technical data for Apple, Vercel and Google services are transferred outside the EU (to the USA). These transfers rely on the European Commission's adequacy decision (EU-US Data Privacy Framework) where the provider is certified, or on EU standard contractual clauses.
10. How long we keep data
- Account and programme data until you delete it. A finished programme stays available (plan, reports, photos, export) until you delete your account.
- After you revoke health data consent, no new data is uploaded and data already uploaded is no longer used for plans or reports. It is not deleted automatically; you delete it under Profile → Data.
- Delete everything deletes the data on the server, encrypted photos, your sign-in account, the data on your phone and the photo key in iCloud Keychain.
- The record of redeemed purchases (only transaction ID and time, with no link to an account) is kept permanently, see Purchases.
- Database backups are made by Supabase. Deleted data may persist in them for a limited time until the backups are overwritten.
- Operational logs are kept by providers only as long as needed for operation and security.
11. Security
- Every database row is protected by access rules (row level security): only you can read it.
- Photos are encrypted on your phone (end-to-end); other data is encrypted at rest by the storage provider.
- Service keys (AI, server administration) live only on the server, never in the app.
- Traffic between the app and the server is encrypted (HTTPS).
12. Your rights
You have the right to access your data, to rectification, erasure, restriction of processing, data portability and to object to processing based on legitimate interest. You can withdraw consent at any time; this does not affect the lawfulness of processing before the withdrawal.
You can do most of this yourself in the app:
- Access and portability: Profile → Data → Export everything. A ZIP archive is created on your phone with all your data as JSON and your decrypted photos.
- Erasure: Profile → Data → Delete everything.
- Rectification: Profile → Profile and plan.
- Withdrawing consent: Profile → Consents.
- What goes where: Profile → About.
For anything else, write to hello@delta12.app. We will reply without undue delay and within one month at the latest.
You also have the right to lodge a complaint with a supervisory authority. In the Czech Republic this is the Office for Personal Data Protection (Úřad pro ochranu osobních údajů), Pplk. Sochora 27, 170 00 Prague 7, uoou.gov.cz. You can also complain to the authority in the country where you live or work.
13. Consents: full text
You give consents in the app at the start of onboarding, each one separately, before the app reads anything from Health. Every change is stored as a new record with the text version and time. Current text version: 2026-09-29. You can revoke and grant them again at any time under Profile → Consents.
Health data required
“We use sleep, heart rate, workouts, weight and limitations to build and evaluate your plan.”
You consent to the processing of health data under Art. 9(2)(a) GDPR: daily summaries from Health, weight, circumferences, performance tests, the questionnaire, the habit diary, maximum heart rate, limitations for the plan and plan completion, for the purpose of building the plan, adjusting it, weekly reports and the final evaluation of the programme.
If you revoke it: the app stops sending daily and weekly Health summaries to the server and no longer pairs Health workouts with your plan. Health data stays readable on your phone. The weekly report and the plan stop using Health data, including what was uploaded before, and work from completion, the questionnaire and what you enter by hand. Data already on the server stays until you delete it in the Data section.
AI processing required
“Your plan and reports are written by AI (EU agreement). We send only summaries and goals – never photos or raw data.”
You consent to us passing the data listed in section 5 (including summaries of health data) to the language model provider Anthropic, including outside the EU, so that it can build your plan, next-week proposals and report summaries.
If you revoke it: the AI stops building your plan, next week's proposals and the AI summary in the weekly report. The report still shows your numbers. Your approved plan stays as it is and you can keep adjusting it yourself.
Anonymous comparison optional
“Anonymised summaries help compare results of programs and coaches fairly.”
You consent to us using your results, after anonymisation, for future comparisons of programme and coach results. We do not run any comparisons yet; the consent is only recorded. The app works the same without it.
If you revoke it: your summaries won't be used for comparisons. Your plan, reports and data in the app aren't affected.
14. Delta12 is not a medical device
Delta12 doesn't diagnose or treat anything and doesn't replace a doctor. Plans and suggestions are about fitness, sleep, habits and nutrition principles. We process health data only so that the plan fits you.
15. Changes to this policy
If we change this policy, we will publish the new version on this page with a new version number and effective date. If a change requires new consent, we will ask for it in the app; consent texts are versioned.