Undertow — Terms of Use
Effective 26 September 2026. Version 1.4.
These terms are an agreement between you and Flapp Bilişim Anonim Şirketi ("we", "us") covering the Undertow iOS app and the service behind it. By subscribing or using the app you accept them. If you do not, do not use Undertow.
These terms describe the separate Undertow account and Gmail connection. Where these terms are silent, Apple's Licensed Application End User License Agreement applies as the default.
1. What Undertow does
The iPhone checks Gmail delivery headers for likely newsletters. After you approve a publication, the iPhone sends bounded text from its issues to Undertow to build a short deck. It is a reading tool for content you already subscribe to. It does not publish, sell, or license any content of its own.
2. Your account and your mailbox
- You must be at least 13 years old, and old enough in your country to enter into this agreement.
- You must own, or be authorised to use, the mailbox you connect. Do not connect an employer's mailbox without permission, and do not connect someone else's mailbox at all.
- You are responsible for keeping your device and Gmail app password secure. The Gmail address stays in app preferences on your iPhone; the app password stays in its Keychain. Neither is given to Undertow. You can revoke the app password separately in your Google Account.
- Keep one account per person. Sharing an account defeats the taste profile anyway.
3. Subscription, price, renewal, and cancellation
Undertow is a paid subscription sold through the App Store. Apple requires these facts to be stated plainly, and they are also just the facts:
- What you get: full access to Undertow — the nightly deck, the taste loop, push delivery, and your archive.
- Length of subscription and price: choose monthly or yearly renewal. The purchase screen shows the current App Store price in your local currency, the billing period, and applicable taxes before you confirm.
- Free trial: when Apple's offer and eligibility check show one for your account, the purchase screen displays its length before you confirm. A prior introductory offer in this subscription group may make you ineligible.
- Payment is charged to your Apple Account at confirmation of purchase, or at the end of the free trial.
- Auto-renewal: the subscription renews automatically unless auto-renew is turned off at least 24 hours before the end of the current period. Your Apple Account is charged for the renewal within 24 hours before the period ends.
- Cancelling: you cancel through Apple, not through us — Settings → your name → Subscriptions → Undertow → Cancel Subscription, or the "Manage subscription" link in Undertow's own Settings screen, which opens the same sheet. Cancelling stops the next renewal; you keep access until the end of the period you have already paid for.
- Unused trial time is forfeited if you buy a subscription while a free trial is running.
- Price changes: Apple handles notices and any consent required for a subscription price change under its App Store rules.
- Refunds are handled by Apple, not by us — reportaproblem.apple.com. We cannot issue a refund for an App Store purchase, though tell us what went wrong anyway and we will help you make the case.
Deleting your Undertow account does not cancel your App Store subscription. Cancel it in Settings as above, or you will keep being billed for a service you have deleted.
4. What we do with your data
The Privacy Policy is part of this agreement. The essentials: Sign in with Apple identifies only the Undertow account; the iPhone opens Gmail over read-only IMAP and checks headers locally; message text is requested only for publications you explicitly approve; bounded, sanitized newsletter text is sent to Undertow and selected excerpts are sent to Anthropic's API and may contain personal information; service-code retention defaults are 30 days for source text and 90 days for generated decks and feedback, but production scheduling and backup handling require verification; and account deletion retains limited tombstone, receipt and ledger records for replay prevention and restore reconciliation.
5. Third-party content, and the limits of a machine editor
Cards are written from newsletters other people wrote. We do not endorse, verify, or take responsibility for what your sources say, and we make no claim to their content beyond showing you short attributed excerpts of issues you are already a subscriber to, always with a link to the original. If you no longer want a publisher's work summarised for you, drop that sender in the app.
Cards are generated by a language model working from those issues. The system is built to make fabrication hard — a card's sources are re-checked against your own stored issues, and a card can only link to an address that appeared in the issue itself — but it is not built to make error impossible. Cards can be wrong, and can be wrong in confident-sounding prose. Use the source link before you act on anything that matters. Undertow is not financial, legal, medical or professional advice.
6. Acceptable use
Do not: resell or redistribute the decks Undertow makes for you; scrape, automate, or hammer the API; attempt to reach another user's data; reverse the service to rebuild a competing product; or connect a mailbox you have no right to. We may suspend an account that does these things, and will tell you why.
7. Availability
Undertow runs a nightly job, not a promise. Some nights produce no deck because nothing was worth reading — that is the product working. Other nights something breaks. We do not offer an uptime guarantee, and outages are not grounds for a pro-rata refund, though we will not be precious about it if the service is meaningfully broken for a meaningful time: write to us.
We may change or discontinue features. If we discontinue the service entirely, we will give you notice with enough time to export what you care about, and we will not renew subscriptions we cannot honour.
8. Your content, our software
Your mailbox content is yours. You grant the app permission to read approved newsletter publications and grant us only the permission we need to run the service for you: to receive, store, process, and send excerpts of those newsletters to the processors listed in the Privacy Policy, for the purpose of building your decks and nothing else. That permission ends when you delete your account.
The app, the server, and the editorial prompts are ours. You get a personal, non-transferable licence to use the app while your subscription is active.
9. Disclaimers and liability
To the fullest extent the law allows, Undertow is provided "as is", without warranties of any kind, and our total liability to you for any claim relating to the service is limited to the amount you paid us in the twelve months before the claim. Nothing here limits liability that cannot lawfully be limited — including, in the EEA and UK, your statutory consumer rights, and in Australia the guarantees under the Australian Consumer Law.
10. Termination
You may stop at any time: cancel the subscription with Apple and delete your account in the app. We may terminate for a material breach of section 6, or if we shut the service down.
11. Apple
Apple is not a party to this agreement. Apple has no obligation to provide support for Undertow, and no responsibility for it or its content. Apple and its subsidiaries are third-party beneficiaries of these terms and may enforce them against you. If the app fails to conform to any warranty Apple is required to give, you may notify Apple and Apple will refund the purchase price; beyond that, Apple has no warranty obligation. Claims about the app — product liability, legal non-compliance, consumer protection, intellectual property — are our responsibility, not Apple's.
12. Changes to these terms
We will change the version and effective date above, and announce a material change in the app before it takes effect. Continuing to use Undertow after that means you accept the new terms; if you do not, cancel and delete.
13. Governing law and contact
These terms are governed by the laws of the Republic of Türkiye, without regard to conflict-of-laws rules, and the courts and enforcement offices of İstanbul have exclusive jurisdiction — except that if you are a consumer in the EEA or the UK, you keep the protection of the mandatory law of your country of residence and may bring proceedings there, and a consumer in Türkiye keeps the right to apply to the consumer arbitration committee or consumer court for their own place of residence.
Flapp Bilişim Anonim Şirketi · undertow@flapp.ist · Evliya Çelebi Mah., Sadi Konuralp Cad., İKSV Vakfı No: 5, İç Kapı No: 2, Beyoğlu / İstanbul, Türkiye