Terms of Service

Last updated: April 2026

Welcome to duiduidui! ("DuiDuiDui", "we", "us", "our"). These Terms of Service ("Terms") are a binding agreement between you and Red Thread Labs LLC that govern your use of the DuiDuiDui mobile application, our websites, and any related services (together, the "Service"). By installing, signing up for, or using the Service, you agree to these Terms. If you do not agree, please do not use the Service.

1. Who can use DuiDuiDui

You must be at least 13 years old to use the Service. If you are under the age of majority in your jurisdiction, you must have your parent or legal guardian's permission to use the Service and to accept these Terms on your behalf. By using the Service, you represent that you meet these requirements.

2. Your account

When you sign up, you'll provide either an email address or phone number and verify it with a one-time code. You are responsible for keeping your login credentials and your device secure, and for all activity that happens under your account. Please notify us promptly if you suspect unauthorized access.

You may also use the Service in an anonymous trial state without providing an email or phone number. Anonymous accounts are tied to a single device and cannot be recovered if the app is uninstalled or the device is lost.

3. Free trial and subscriptions

DuiDuiDui is a paid subscription service. New users receive a free trial period (currently seven days) beginning when their account is created. After the trial ends, continued access to premium features requires an active subscription.

Subscriptions are purchased through the Apple App Store or other authorized channels and are billed to the payment account on file with the app store. Subscriptions renew automatically at the end of each billing period unless you cancel at least 24 hours before renewal. You can manage or cancel your subscription in your Apple account settings.

Refunds, where applicable, are handled according to the refund policies of the app store that sold you the subscription. We do not issue refunds directly.

Trial and subscription terms, including price and duration, may change over time. Any change takes effect at your next renewal.

4. License to use the Service

We grant you a personal, limited, non-exclusive, non-transferable, revocable license to use the Service for your own non-commercial language learning. You may not:

  • Copy, modify, reverse engineer, decompile, or create derivative works from the Service, except to the extent that applicable law expressly permits such activity.
  • Rent, lease, sublicense, sell, or otherwise commercially exploit the Service or its content.
  • Use automated systems to access the Service or extract its content in bulk.
  • Interfere with the Service's normal operation, attempt to bypass access controls, or use the Service to transmit malware.

5. Acceptable use and zero tolerance for objectionable content

We have zero tolerance for objectionable content or abusive users. You agree that you will not, and will not allow anyone using your account to:

  • Post, upload, submit, transmit, or otherwise make available any content that is unlawful, harmful, harassing, defamatory, obscene, sexually explicit, threatening, hateful, or discriminatory.
  • Impersonate any person or entity, or misrepresent your affiliation with any person or entity.
  • Harass, intimidate, stalk, bully, or threaten another user.
  • Use display names, usernames, profile photos, or avatars that are offensive, sexually explicit, or infringe on the rights of others.
  • Solicit personal information from minors, or engage in any activity that exploits or endangers minors.
  • Use the Service to promote or facilitate illegal activity.
  • Use the Service to spam, phish, or deceive other users.

Violations of this section may result in immediate account suspension or termination without notice, removal of offending content, and, where appropriate, reporting to law enforcement.

6. User-generated content

The Service allows you to submit content, including a display name, username, profile photo, and messages to our AI tutor ("User Content"). You retain ownership of your User Content. By submitting it, you grant us a worldwide, non-exclusive, royalty-free license to host, store, reproduce, display, and process your User Content solely for the purpose of operating and improving the Service.

You represent that you have the rights necessary to submit your User Content and that it does not violate these Terms or any law.

7. Reporting and moderation

If you encounter content or behavior that violates these Terms, please use the in-app "Report User" feature on a friend's profile or the flag icon on an AI chat response, or email us at abuse@duiduidui.app.

We review reports and aim to respond within 24 hours. We may, at our sole discretion and without prior notice, remove User Content that we believe violates these Terms, restrict access to features, suspend or terminate accounts, and take any other action we consider appropriate. We may also cooperate with law enforcement requests as required by applicable law.

8. AI-generated content

DuiDuiDui includes an AI tutor powered by large language models. Responses from the AI tutor are generated automatically and may occasionally be inaccurate, inappropriate, or not reflect our views. We do our best to filter unsafe outputs, but we cannot guarantee every response. Use AI-generated content as a learning aid, not as a substitute for professional advice. If you encounter an AI response that is offensive or clearly wrong, please flag it using the in-app flag icon.

9. Intellectual property

The Service, including all software, dictionary content, audio recordings, images, text, logos, and trademarks (other than User Content), is owned by Red Thread Labs LLC or our licensors and is protected by copyright, trademark, and other laws. Except for the limited license granted in these Terms, no rights are transferred to you.

10. Privacy

Our Privacy Policy describes how we collect, use, and protect personal information. By using the Service, you agree to the practices described in the Privacy Policy.

11. Third-party services

The Service may interoperate with third-party services including Apple's App Store, Apple In-App Purchase, and AI providers used to power the tutor. Your use of those services is subject to their own terms and policies.

12. Disclaimers

The Service is provided "as is" and "as available", without warranties of any kind, whether express or implied. To the fullest extent permitted by law, we disclaim all warranties, including merchantability, fitness for a particular purpose, non-infringement, and accuracy. We do not warrant that the Service will be uninterrupted, secure, or error-free, or that any content (including dictionary content and AI-generated output) is complete, accurate, or up to date.

13. Limitation of liability

To the fullest extent permitted by law, Red Thread Labs LLC and its officers, employees, and agents will not be liable for any indirect, incidental, special, consequential, exemplary, or punitive damages, or any loss of profits, revenue, data, or goodwill, arising out of or in connection with your use of the Service. Our total aggregate liability for any claim arising out of or relating to these Terms or the Service will not exceed the greater of (a) the amounts you paid us in the twelve months preceding the claim, or (b) US$50.

Some jurisdictions do not allow the exclusion of certain warranties or limitations on liability, so some of the above limitations may not apply to you.

14. Indemnification

You agree to indemnify and hold harmless Red Thread Labs LLC, its affiliates, and their respective officers, employees, and agents from any claims, damages, liabilities, and expenses (including reasonable attorneys' fees) arising out of your violation of these Terms, your misuse of the Service, or your violation of any law or the rights of a third party.

15. Termination

You may stop using the Service at any time. We may suspend or terminate your access to the Service, with or without notice, if you violate these Terms or if we discontinue the Service. Sections of these Terms that by their nature should survive termination (including sections 4, 6, 9, 12, 13, 14, and 17) will survive.

16. Changes to these Terms

We may update these Terms from time to time. When we make material changes, we'll notify you in the app or by email. Continued use of the Service after the changes take effect means you accept the updated Terms.

17. Governing law and disputes

These Terms are governed by the laws of the State of Oregon, United States, without regard to conflict-of-laws principles. Any dispute arising out of or relating to these Terms or the Service will be resolved in the state or federal courts located in Clackamas County, Oregon, and you consent to the personal jurisdiction of those courts.

18. Contact

Questions about these Terms, or reports of abuse or objectionable content, should be sent to abuse@duiduidui.app or support@duiduidui.app.