4Form AI Privacy Policy
Effective: 2 September 2026 Last updated: 2 September 2026
The short version
- Your videos never leave your phone. Analysis happens on your device. We never receive, store, or see your footage.
- What we do receive are measurements: joint angles and movement statistics, plus your account details and what you type into the app.
- We don't sell your data, and we don't advertise.
- You can delete your account and everything in it from inside the app, at any time, without contacting us.
1. Who we are
4Form AI is operated by Tyson Youm and Oscar Chuang. There is no office and no postal correspondence. Every route to us is by email, and each address below reaches a person. Questions: privacy@4formai.com
For UK/EU users, Tyson Youm and Oscar Chuang is the data controller for the information described here.
2. What we collect
Information you give us
| Data | Why | Kept |
|---|---|---|
| Email address | Sign-in, password reset, security notices | Until you delete your account |
| Password | Sign-in. Stored only as a bcrypt hash, which we cannot read | Until you delete your account |
| Name | Shown in the app | Until you delete your account |
| Date of birth | Checking you are old enough to use the app (see §9). Required on both ways of signing up, and kept afterwards rather than discarded once checked, so the check can be re-verified. We store the date only, never a time | Until you delete your account |
| If you sign in with Apple or Google: the account identifier that provider gives us, and the email address it tells us | Recognising you as the same person on your next sign-in, and letting support see which provider your account uses. With Apple this address may be a private relay address rather than your own | Until you delete your account |
| Sport, level, goals, injury concerns | Tailoring your coaching notes | Until you delete your account |
| Session titles | Labelling your own sessions | Until you delete your account |
| Messages to the AI coach | Answering them, and continuity between messages | Until you delete your account |
| Email address, if you join the waitlist on 4formai.com | Sending you one email when the TestFlight build opens | Until the build opens, or until you ask us to remove it |
Information created when you analyse a clip
When you pick a training video, the app measures your body position on your device. What is sent to us is the resulting numbers:
- joint angle ranges, averages, and variability
- left/right symmetry
- how much of the clip each joint spent outside its typical range
- clip length, frame count, and tracking quality
- the technique scores computed from the above
The video itself is never uploaded. It is copied into your app's private storage so the skeleton overlay can replay it, and it stays there until you delete the session or uninstall the app.
Information collected automatically
- Device IP address, used transiently for rate limiting and abuse prevention. Not used to build a profile of you.
- Error and diagnostic logs. We deliberately exclude request bodies from logs, so passwords, reset tokens, and message contents are not captured.
What we do not collect
- Your video footage
- Photos or media other than the clip you explicitly pick. If you set a profile photo, it is stored only on your device and is never uploaded; removing it, or deleting your account, deletes it from the device.
- Location
- Contacts, calendar, microphone, or camera
- Advertising identifiers
- Any biometric identifier used to identify *who you are* (see §3)
3. A note on what the measurements are, and are not
The app measures how a body moves in a video: angles between limbs over time. It does not perform facial recognition, fingerprinting, or any form of identification from your body. The measurements cannot be used to recognise you in another video, and we do not attempt to.
Some jurisdictions (notably Illinois' BIPA, Texas' CUBI, and Washington's HB 1493) define "biometric identifier" broadly. Our position is that movement measurements are not biometric identifiers, because they are not used, and are not usable, to identify an individual. We state it plainly here so you can judge for yourself.
4. Why we're allowed to use it (UK/EU legal bases)
| Purpose | Legal basis |
|---|---|
| Running your account, delivering analysis | Performance of a contract |
| Security, rate limiting, abuse prevention | Legitimate interests |
| Improving the product | Legitimate interests |
| Using what you tell us about your injuries, and any injury-related goal you pick, to shape your coaching notes | Your consent (Art. 6(1)(a)), and your explicit consent to the processing of health data (Art. 9(2)(a)) |
| Anything else we ask you about | Consent, which you may withdraw |
On the injury information. What you tell us about your knees, hips, lower back, shoulders, elbows or ankles is information about your health, and so is choosing "Return from injury" or "Stay injury-free" as a goal. UK/EU law treats health data as a *special category*: an ordinary legal basis is not enough by itself, and a second condition from Article 9 has to sit on top of it. The condition we rely on is your explicit consent, Article 9(2)(a). It covers those two items and nothing else in this policy. Your measurements, scores and risk flags are not health data in our view, for the reasons in §3.
Concretely, that consent is the answer you give during onboarding, at the step that asks whether anything is giving you trouble. Choosing "None right now" stores nothing at all. We do not infer injuries from your measurements, and no other part of the app writes to that field. When it is set, it goes to Anthropic along with your analysis (§5).
You can withdraw it. Deleting your account removes it immediately, from inside the app, without contacting us (§8). The app does not yet have a screen that clears the answer while keeping your account, so until it does, write to privacy@4formai.com and we will clear it for you.
5. Who else sees it
We do not sell your personal information. We do not share it for advertising. We use a small number of processors, each doing one job:
| Processor | What they get | Why |
|---|---|---|
| Railway | Everything stored, as our infrastructure | Running the API |
| Supabase | The database contents | Storing your account and measurements |
| Anthropic (Claude) | Your measurements and scores, your sport, level, goals and injury concerns, the title you typed for the session, your coach messages, and the coaching notes we wrote for your two most recent sessions in the same sport | Writing your coaching notes and replying in chat |
| Resend | Your email address | Sending password resets and security notices |
On Anthropic: this happens in two places, and they send different things.
When a clip is analysed, we send the measurements and scores from that clip, the sport and level on your profile, the session title you typed, your stated goals, your injury concerns if you have given any, and the coaching notes we wrote for your two most recent completed sessions in the same sport, so the coach builds on what it already told you instead of repeating it. When you write to the coach in chat, we send the last ten messages of that conversation, your sport and level, and the title, scores, strengths and improvements from your most recent measured session.
Your video is not sent: Anthropic receives numbers and text, never footage. Your name, email address and date of birth are not sent either, and neither is anything from your Apple or Google sign-in. Under Anthropic's commercial terms, this data is not used to train their models.
We may also disclose information where legally required, or to protect the rights and safety of our users.
6. Where it lives
4Form AI is operated from the United States. Your data is stored in Canada (Supabase, ca-central-1). The other companies that handle it for us are listed in §5, and some of them are in the United States.
If you are in the UK or EU, your data therefore moves between countries. We have a data processing agreement with each of the four companies in §5 (Railway, Supabase, Anthropic and Resend), and every one of them incorporates the European Commission's Standard Contractual Clauses, and the UK addendum to them where UK data is involved. If you would like a copy of those arrangements, write to privacy@4formai.com and we will send them.
There used to be a fifth name here. The pose-tracking library that measures your video was downloaded from jsDelivr, a free public CDN we had no contract with, which meant your device's IP address went to a company we could make you no promises about. We now serve that library from our own API instead, so the only companies your device contacts are the four above.
7. How long we keep it
Your data stays until you delete it. When you delete your account, your account row (including your date of birth and any Apple or Google sign-in link) and your profile, analyses, measurements, coaching notes and chat history are removed. A copy can survive for a short time in our database provider's routine backups, which are overwritten on a rolling schedule. No backup is kept for longer than 30 days, so a deletion is complete everywhere within 30 days of your request, and usually sooner. Anonymous, aggregated statistics that cannot identify you may be retained.
8. Your choices and rights
In the app, right now:
- Delete your account and all your data: Profile → Delete account. Takes effect immediately and needs no email to us.
- Delete a single session: swipe it away in your sessions list.
- Delete a clip: it is a file on your device; deleting the session removes it.
On request, at privacy@4formai.com: access a copy of your data, correct it, restrict or object to processing, withdraw a consent you have given (including the injury information covered by §4, which we will clear for you), or receive it in portable form. We respond within 30 days.
UK/EU users may complain to their supervisory authority (in the UK, the ICO). California residents have rights under the CCPA/CPRA, including the right to know, delete, and correct, and the right not to be discriminated against for exercising them. We do not sell or share personal information as those terms are defined by the CPRA.
9. Children
4Form AI is not directed at children under 13, and we do not knowingly collect their information. If you believe a child under 13 has given us data, write to privacy@4formai.com and we will delete it.
Users aged 13–17 should have a parent or guardian read this policy and the Terms with them. See the Terms of Service for the age requirements that apply to using the app.
10. Security
Passwords are hashed with bcrypt at cost 12 and are never stored, logged, or transmitted in a readable form. Accounts lock after repeated failed sign-ins, and you are emailed when that happens. Your session token is held in your device's secure keychain. All traffic uses HTTPS. Resetting your password signs out every existing session.
No system is perfectly secure, and we don't claim otherwise. If you find a vulnerability, please write to security@4formai.com.
11. Changes
We will update the date at the top when this changes. For anything that materially affects your rights, we will tell you in the app before it takes effect.
12. Contact
privacy@4formai.com · Tyson Youm and Oscar Chuang