Terms of use

Last updated: 11 October 2026

1. Agreement and acceptance

These terms (version 2026-10-11) are an agreement between you and Seyfi Can Zeyrek, an individual developer in Türkiye who publishes Duet as Morrowline on Google Play ("we", "us"). They cover the Duet app for iPhone and Android, its home-screen and lock-screen widgets, its notifications, Couple Pro and the invite web page we host. Our privacy policy applies together with these terms.

By tapping Agree and continue on the welcome screen, which links to these terms and to the privacy policy, and by downloading, installing or using Duet, you accept these terms. The privacy policy explains how we handle your data; tapping the button is not an agreement to it. We store the version of the terms you accepted and the time you accepted them. If you do not agree, do not use Duet.

2. Definitions

App means the Duet app and its widgets.
Service means the App, the servers behind it and the notifications and invite page we provide.
Partner means the one other person whose Duet you pair with.
Shared space means the notes, drawings, photos, widgets, places, games, answers, pet and other things the two of you add once paired.
Content means anything you add to the App.
Couple Pro means the paid subscription that removes the limit on creating new things.
Free moments means the number of creating actions each person can use before Couple Pro is needed.
Stores means the Apple App Store and Google Play.

3. Eligibility and age

You must be at least 13 years old to use Duet, and old enough under the law of your country to enter this agreement. If you are under the age of majority where you live, a parent or guardian must agree to these terms for you. Local minimum ages for online services still apply. Duet is not directed to children.

4. Your account

The app creates an anonymous account identifier when you first open it; it is not tied to your name unless you add one. You do not register with an email address or a password. You add a first name or nickname so your Partner knows who you are.

The identifier is stored on your phone and on our servers. On iPhone it can survive a reinstall in the system keychain, and on Android Auto Backup can restore it; if neither applies to your phone, losing the phone means losing access to the account. You are responsible for what happens on your device, so keep it locked. One identifier belongs to one person and must not be shared.

You can delete your account at any time in Settings > Delete account, as described in the privacy policy.

5. License to use the app

We give you a personal, non-exclusive, non-transferable and revocable licence to use the App on devices you own or control, for private, non-commercial use, under these terms and the rules of the Store you downloaded it from. You must not copy, modify or sell the App, reverse engineer it except where the law allows, or circumvent its technical limits. All rights not granted stay with us and our licensors.

If you downloaded the app from Google Play, Google is not a party to these terms. Purchases are processed under Google Play's terms of service. These terms do not give you rights against Google.

6. Apple App Store terms

If you downloaded the app from the Apple App Store, the following also applies:

Acknowledgement. These terms are between you and Seyfi Can Zeyrek only, not with Apple Inc. ("Apple"). We, and not Apple, are solely responsible for Duet (the "Licensed Application") and its content. These terms do not override Apple's Media Services Terms and Conditions.
Scope of licence. The licence we grant you is non-transferable and limited to Apple-branded products that you own or control, and as permitted by the Usage Rules set out in Apple's Media Services Terms and Conditions (including use through Family Sharing or volume purchasing where Apple allows it).
Maintenance and support. We, and not Apple, are solely responsible for maintenance and support of the Licensed Application, as set out in these terms or as required by law. Apple has no obligation to provide maintenance or support.
Warranty. If the Licensed Application fails to conform to an applicable warranty, you may notify Apple, and Apple will refund the purchase price for the Licensed Application to you (if any). To the maximum extent permitted by law, Apple has no other warranty obligation for the Licensed Application. Other claims, losses, liabilities, damages, costs or expenses caused by a failure to conform to a warranty are our responsibility.
Product claims. We, and not Apple, are responsible for addressing claims by you or a third party relating to the Licensed Application or your possession and use of it, including product liability claims, claims that it fails to meet a legal or regulatory requirement, and claims under consumer protection, privacy or similar laws. Nothing in these terms limits our liability beyond what the law allows.
Intellectual property. If a third party claims that the Licensed Application or your possession and use of it infringes that party's intellectual property rights, we, and not Apple, are solely responsible for the investigation, defence, settlement and discharge of the claim.
Legal compliance. You confirm that you are not located in a country that is subject to a US Government embargo or designated by the US Government as a "terrorist supporting" country, and that you are not on any US Government list of prohibited or restricted parties.
Developer contact. Questions, complaints or claims about the Licensed Application can be sent to Seyfi Can Zeyrek, Esenyalı Mahallesi, İzmir, Türkiye, e-mail address zeyrekseyfican@gmail.com.
Third-party terms. You must comply with the third-party terms that apply when you use the Licensed Application (for example, the terms of your mobile data provider).
Third-party beneficiaries. Apple and its subsidiaries are third-party beneficiaries of these terms. Once you accept them, Apple has the right (and is considered to have accepted the right) to enforce these terms against you as a third-party beneficiary.

7. Device permissions

Duet asks for permissions only for the features that need them: location while the app is open, notifications, the camera for a profile photo and your photos for pictures you choose. You may refuse or revoke any permission in your system settings at any time. Some features stop working without the matching permission, and the core app does not depend on any of them. Details are in the privacy policy.

8. The service and its limits

Duet helps two partners stay close with a shared space, widgets on their home screens, notes, miss-you pings, drawings, places, games, a daily question and a shared pet. Features, content and limits can change as we improve the Service.

Duet does not show ads and does not use your data for advertising.

Some things are free and some need Couple Pro. Reading and viewing stay available; creating new notes, nudges, doodles, answers, pet care, games, places and widgets needs Couple Pro once your free moments are used up. We show what a purchase unlocks before you buy.

Distances, counts, streaks and other figures in Duet are calculated from the data you and your partner provide and can be wrong or out of date. Distances use a location rounded to about 1 km.

The Service depends on your device, your operating system, your connection and services run by others, such as the Stores and the push services of Apple and Google. Notifications, widget refreshes and sealed notes can arrive late or not at all. We do not promise uninterrupted or error-free operation, and we do not promise any outcome for your relationship.

Home-screen and lock-screen widgets can show your notes, drawings, photos, names, countdowns and distance to anyone who can see your screen.

9. Linked accounts and sharing

You can pair with one Partner. Pairing needs their action: they accept your invite code or link, after seeing who invited them. Either of you can pause Duet, which switches nudges off, and either of you can resume it.

Anything you add to a shared space (notes, pings, drawings, photos, widgets, places, answers, your status, when you were last active and the distance between you) is visible to the person you are paired with.

If you unpair, your stored location, game rounds, next meetup and shared streak are cleared, and the notes, drawings, places, pet and photos you added stay with your partner. Deleting your account has the effects described in the privacy policy.

Only share another person's information, photos or location with their agreement. Do not use Duet to watch, track or pressure someone who has not agreed, and do not pair a phone or identifier you do not control. Location is shared with your Partner only if you allow location access on your own phone, and you can stop it with Share my distance in Settings or in your device settings. If you feel unsafe because of how Duet is used, write to zeyrekseyfican@gmail.com; we can remove a pairing, limit features or suspend an account.

10. Your content

You keep ownership of your Content. To run the Service you give us a worldwide, non-exclusive, royalty-free licence to host, store, copy, resize, display and transmit your Content to your Partner and to our service providers, for the time you keep it in the App, and only to operate and secure the Service.

You confirm that you have the rights to your Content and the consent of the people in it. We may remove Content or limit access if it breaks these terms or the law. You can delete your own notes, drawings and places in the App, and what happens to copies is described in the privacy policy.

11. Acceptable use

You must not:

use Duet for anything unlawful, or to harass, threaten, stalk or impersonate anyone;
share another person's private data, photos or location without their consent, or monitor someone who has not agreed;
upload sexual content involving minors, malware or content that infringes the rights of others;
bypass the limits or the paywall, resell access, scrape or access Duet by automated means, or abuse invites or notifications to bother others;
break export control or sanctions law.

If you break these terms we may warn you, limit features or suspend access. Report problems at zeyrekseyfican@gmail.com.

12. Purchases and subscriptions

Couple Pro is sold as weekly and annual subscriptions through the Apple App Store or Google Play. The price and billing period are shown in the Store before you buy, and taxes may apply. Payment is charged to your Store account when you confirm the purchase and again at each renewal.

Subscriptions renew automatically until you cancel in your App Store or Google Play account settings. Cancel in your Apple ID settings (App Store > Subscriptions) or in Google Play (Payments & subscriptions > Subscriptions), at least 24 hours before the period ends on Apple, or before the renewal date on Google Play. Deleting the app or your account does not cancel a subscription. After cancelling you keep Couple Pro until the end of the paid period.

Couple Pro comes from a store subscription held by either of you: while you are paired one subscription covers both of you, and if you unpair, access follows the person who holds the subscription.

Reading and viewing stay available; creating new notes, nudges, doodles, answers, pet care, games, places and widgets needs Couple Pro once your free moments are used up. If you have no free moments left, you can send your Partner a notification asking them to unlock Couple Pro.

Apple and Google handle payments and refunds under their own rules, and we cannot refund store purchases ourselves. This does not affect rights you have by law. Use Restore in the App with the same Store account to get Couple Pro back on a new device. If the price of a subscription changes, the Store tells you before the change applies and you can cancel before it takes effect. We do not store your card details; the Store processes the payment.

13. Third-party services

Duet depends on third-party services: the Stores, the push services of Apple and Google, Google's Firebase, RevenueCat, and, for Our places, the Photon search service run by komoot and the OpenFreeMap map service. The App may also open links, such as the Store subscription pages or your share sheet. These services are not ours; their own terms apply, and we are not responsible for their content, availability or practices. Open-source components are used under their licences, which the App lists.

14. Intellectual property

We and our licensors own the App, its design, text, illustrations, the pet and its artwork, our names and logos, and all related intellectual property rights. You get no right to use our trademarks. If you send us feedback, we may use it without owing you anything.

15. Privacy

The privacy policy at https://duet.morrowline.app/en/privacy/ explains how we handle personal data and applies to your use of the App. Users in Türkiye can also read the separate information notice under the Turkish data protection law (KVKK) at https://duet.morrowline.app/en/kvkk/.

16. Your rights as a consumer

Nothing in these terms limits rights you have as a consumer under the law of the country where you live and that cannot be waived by agreement.

If you buy Couple Pro as a consumer in the EU or UK, you have a 14-day right to withdraw from a distance contract. For digital content supplied immediately, you lose this right if you expressly asked for immediate supply and acknowledged that you lose it. For digital services, if you asked us to start during the withdrawal period you pay a proportionate amount for the service used. In the Store's purchase flow you can request a refund; the Store's withdrawal or refund function is available during the 14 days.

Digital content and services must be as described, of satisfactory quality and fit for purpose. If they are not, you may be entitled to repair, a price reduction or termination under EU Directive 2019/770 or the UK Consumer Rights Act 2015.

In Türkiye, your rights under Law no. 6502 on Consumer Protection and its regulations, including rights relating to distance contracts and unfair terms, remain in force.

17. Disclaimer of warranties

The app and the service are provided "as is" and "as available". We do not promise that they will be uninterrupted, error-free or suitable for a particular purpose. Rights that the law gives you and that cannot be excluded remain. For iOS, Apple's refund route in the Apple terms above applies.

18. Limitation of liability

We are not liable for indirect or consequential loss, lost profits, lost data or loss of goodwill, to the extent the law allows. Our total liability to you for all claims about the app is limited to the amount you paid us for the app in the 12 months before the event, or 50 euros if you paid nothing, to the extent the law allows.

Nothing limits liability for death or personal injury caused by negligence, for fraud or fraudulent misrepresentation, for intent or gross negligence, or for anything that cannot be limited by law, including your statutory consumer rights. This section does not limit Apple's refund route in section 6 or our responsibilities under clauses 4 and 5 of the Apple terms.

19. Termination

You can stop using Duet at any time and delete your account in Settings > Delete account. Deleting the app does not delete your account or cancel a subscription.

We may suspend or end your access if you seriously or repeatedly break these terms, if the law requires it, or to protect others. We tell you in advance where practical.

When your access ends your licence ends. What happens to your data is described in the privacy policy, and Couple Pro is handled through the Store. Sections about intellectual property, liability, disputes and anything meant to continue stay in force.

20. Governing law and disputes

Talk to us first. If you have a complaint, write to zeyrekseyfican@gmail.com. We will try to resolve it within 30 days before either of us starts formal proceedings. This does not affect your right to go to court or to a consumer authority at any time.

Governing law. These terms are governed by the laws of Türkiye, without regard to conflict-of-law rules. If you are a consumer, mandatory consumer protection rules of the country where you live continue to apply to you.

Courts. The courts of Türkiye have non-exclusive jurisdiction. If you are a consumer, you may also bring a claim in the courts of the place where you live, and we can only bring a claim against you in the courts of that place, to the extent the law of your country says so. In Türkiye, consumer courts and consumer arbitration committees of your place of residence remain available to you under Law no. 6502. Small-claims procedures where you live remain available to you.

There is no arbitration clause and no class-action waiver in these terms.

21. Changes to these terms

We may change these terms, for example when we add features. We will tell you in the app and update the date above. Material changes take effect after notice, at least 30 days where we can give it. If you keep using Duet after the effective date, you accept the changes; if you disagree, you can stop using Duet and delete your account. Where the law requires your consent, we ask for it.

22. General

If a part of these terms is unenforceable, the rest stays in force. If we do not enforce a right, we do not waive it. These terms and the privacy policy are the entire agreement between us about Duet. We may assign these terms to a successor that takes over Duet. We may give notices in the app or by e-mail where we have an address. You may not assign these terms without our consent. Nobody else has rights under these terms, except Apple as stated in section 6.

23. Contact

Seyfi Can Zeyrek (individual developer; publisher name on Google Play: Morrowline), Esenyalı Mahallesi, İzmir, Türkiye. Contact email: zeyrekseyfican@gmail.com. We reply to messages as soon as we can.

Trader identification for EU consumers: Seyfi Can Zeyrek, Esenyalı Mahallesi, İzmir, Türkiye, zeyrekseyfican@gmail.com.