Last updated November 6, 2026.
Stack is run by Dad with Style OÜ, Sepapaja tn 6, Tallinn 15551, Estonia (registry code 14696867). These terms are the agreement between you and us for the iPhone app and the web app. By making an account or using Stack, you agree to them.
Our privacy policy says what we do with your data. Write to [email protected] about anything in these terms, or call +372 5705 1822.
You must be 18 or older. One account is for one person. If we learn a user is under 18, we close the account and delete the data.
Stack doesn’t give medical advice. Check with your doctor before any medical decision.
Stack is for general fitness and wellbeing in healthy adults. It isn’t a medical device and doesn’t diagnose, treat, prevent or monitor any disease. In an emergency, call your local emergency number. Training carries a risk of injury. You choose what you lift, how hard you push and what you eat, and you do it at your own risk. If something hurts, stop.
Some of what Stack shows you is an estimate: the calories and nutrients in a food from a photo, a sentence, a menu or a database, your targets, and the programs it builds. An AI model makes some of these estimates, and any of them can be wrong. Check what Stack logs and correct it when it’s off.
Keep your sign-in to yourself. You’re responsible for what happens in your account.
What you enter is yours: your entries, photos and notes. You let us store, copy and show it to run and improve Stack, as our privacy policy says. That permission ends when you delete it or your account; backup copies are gone within 14 days.
The words you searched or said, the food you kept and your corrections are kept without your name, your account or a diary date, so they improve the answers for everyone. They stay after you delete your account, with no link to it.
Stack itself, its code, design, words and food data, belongs to us or to those who license it to us. Use it for yourself; don’t copy, sell or rent it.
Don’t use someone else’s account or let anyone use yours. Don’t enter another person’s data without their permission, or upload anything illegal or that isn’t yours to share. Don’t try to break into Stack, get around its limits, overload it, or copy its data in bulk or with automated tools.
If you do, we may suspend or close your account. We tell you first and say why, unless the law or someone’s safety needs us to act at once.
You buy a subscription in the iPhone app, through Apple, and pay with your Apple account. The price, how often it renews and any free trial are shown in the app before you confirm.
When a subscription ends, the parts of Stack it pays for stop. Your records stay until you delete them or your account.
If your coach is another business, we provide the app, not the coaching: that coach is independent of us and alone responsible for their advice, and your coaching, its price and how it ends are between you and them. If your coach is us (Founder Athlete OS), your coaching agreement governs the coaching. These terms cover only the app. Your coach can see what you enter, as our privacy policy says.
When coaching ends, your app closes and your records stay, so your history is there if you come back. Our privacy policy says for how long. Ask your coach or write to us to have it deleted.
You can connect an AI you already use in Settings, then Connect your AI. The link works like a password: whoever has it can read your data, so keep it to yourself. Making a new link stops the old one at once.
Your AI is run by another company, under its own terms. What it tells you and what it does with your data are up to that company, not us. A program your AI builds waits as a draft until you tap Use it.
Delete your account in the app at any time: Settings, then Privacy, then Delete my account. Your records go at once, and it can’t be undone.
We work to keep Stack right and running, but we can’t promise it is always available or free of mistakes.
Nothing in these terms limits responsibility that the law doesn’t let us limit, such as for harm caused on purpose or by gross negligence, or death or injury. If you use Stack as a consumer, we are responsible for foreseeable loss caused by our breach, up to what you paid for Stack in the 12 months before your claim, or 100 euros if that is more. If you use it for business, our total responsibility is what you paid for Stack in the 12 months before your claim, or 100 euros if that is more. Nothing here limits responsibility under data protection law. If you live in the United States, Stack is provided as is, without implied warranties, as far as your state’s law allows, and you accept the risk of training.
Nothing in these terms takes away your rights as a consumer, including your right to an app that works as described.
We give you a personal license, which you can’t pass on, to use the iPhone app on Apple devices you own or control, as Apple’s rules for the App Store allow.
These terms are between you and us, not Apple. Apple isn’t responsible for the app or its content and doesn’t support or maintain it. If the app doesn’t work as described, you can tell Apple, and Apple refunds what you paid for it; beyond that, as far as the law allows, Apple owes you nothing for it. Any claim about the app, including that it breaks a law or someone’s rights in their work, is ours to handle, not Apple’s.
You confirm you aren’t in a country under a US government embargo or on a US list of prohibited or restricted people, and you keep to your phone and internet provider’s terms when you use the app. Apple and its subsidiaries can enforce these terms.
We may change Stack, or these terms, for these reasons: a new law, or a requirement of a regulator or Apple; security; a new or changed feature; or a fault. We tell you in the app or by email at least 30 days ahead, saying what changes and when. A change costs you nothing extra. If it makes Stack worse for you in more than a small way, you can end your subscription free of charge within 30 days of our notice or of the change, whichever is later, and get back what you paid for time you haven’t used: ask Apple at reportaproblem.apple.com, and if Apple doesn’t refund it, write to us and we will. Apple shows any price rise before it applies, and you can cancel first. We may transfer these terms to a buyer of Stack; your rights stay the same. If part of these terms is invalid, the rest stands. These terms are the whole agreement between us about the app.
Estonian law applies to these terms. If you use Stack as a consumer, you keep the protections the law where you live gives you, and you can take a claim to the courts where you live. Write to us first and we’ll try to put it right.
If we can’t settle a complaint, you can take it to the Consumer Disputes Committee (Tarbijavaidluste komisjon) at Estonia’s Consumer Protection and Technical Regulatory Authority, Endla 10A, 10122 Tallinn, ttja.ee. It’s free. You agree to receive these terms and our information in English.