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Lingdow

Privacy Policy

Last updated: March 20, 2026

Lingdow ("we", "our", or "us") is committed to protecting your privacy. This Privacy Policy explains how we collect, use, disclose, and safeguard your information when you use our mobile application and related services (collectively, the "Service"). By using the Service, you consent to the data practices described in this Privacy Policy. If you do not agree with the terms of this Privacy Policy, please do not access or use the Service.

1. Information We Collect

We collect several types of information from and about users of our Service, including the categories described below.

1.1 Account Information

When you create an account, we collect your email address and authentication credentials. If you sign in through a third-party service (such as Google Sign-In), we receive basic profile information from that provider, which may include your name, email address, and profile picture URL. We do not receive or store your Google account password.

1.2 Usage Data

We automatically collect certain information when you use the Service, including:

  • Videos you watch, browse, and interact with
  • Words and sentences you save to your vocabulary lists
  • Language preferences, learning settings, and interface language
  • Watch history and video progress timestamps
  • Shadow reading practice sessions and scores
  • Subtitle search queries
  • Feature usage patterns and frequency
  • App session duration and time spent on various features

1.3 Device Information

We collect information about the device you use to access the Service, including:

  • Device model and manufacturer
  • Operating system type and version (e.g., iOS 17.0)
  • Unique device identifiers (such as IDFV - Identifier for Vendors)
  • App version and build number
  • Device language and locale settings
  • Time zone
  • Network connection type (Wi-Fi or cellular)

1.4 Speech Data

When you use the shadow reading feature, audio recordings are processed on-device using Apple's Speech Recognition framework for speech-to-text conversion and pronunciation evaluation. Audio data is processed locally on your device and is not transmitted to our servers. We do not store your voice recordings. Only the resulting text transcription and pronunciation scores are retained to display your practice results.

1.5 Translation and AI Query Data

When you use our word lookup, sentence translation, or AI-powered features, the text you submit (such as words, phrases, or sentences) is sent to third-party AI and translation services for processing. We do not persistently log the content of these queries on our own servers beyond what is necessary to deliver the response to you in real time.

1.6 Subscription and Purchase Information

If you purchase a subscription, Apple processes and stores your payment information. We do not collect, store, or have access to your credit card number, bank account details, or other financial information. We receive from Apple a transaction receipt, subscription status, expiration date, and product identifier to manage your access to premium features.

1.7 Information You Provide Directly

We collect information you provide when you contact our support team, submit feedback, report a problem, or otherwise communicate with us, including your email address and the content of your message.

2. How We Use Your Information

We use the information we collect for the following purposes:

  • Providing the Service: To operate, maintain, deliver, and improve the features and functionality of the Service, including generating bilingual subtitles, AI-powered translations, word definitions, and example sentences.
  • Personalization: To personalize your learning experience, including recommending content based on your language level, preferences, and learning history.
  • Progress Tracking: To track and display your learning progress, vocabulary lists, saved sentences, and watch history.
  • Account Management: To create, maintain, and secure your account, and to authenticate your identity.
  • Subscription Management: To verify your subscription status, manage access to premium features, and process renewals.
  • Communications: To send you service-related communications, such as account verification emails, security alerts, subscription reminders, and responses to your inquiries.
  • Analytics and Improvement: To understand how users interact with the Service, identify trends, diagnose technical issues, and improve the quality and performance of the Service.
  • Legal Compliance: To comply with applicable laws, regulations, legal processes, or enforceable governmental requests.
  • Safety and Security: To detect, prevent, and address fraud, abuse, security risks, and technical issues.

3. Third-Party Services and SDKs

We use the following third-party services to operate the Service. Each of these services may collect information as described in their own privacy policies:

3.1 Supabase (Authentication and Database)

We use Supabase to manage user authentication (email/password and Google Sign-In) and to store user data such as account information, vocabulary lists, saved sentences, and learning preferences. Supabase processes and stores data on secure cloud servers. For more information, see the Supabase Privacy Policy.

3.2 OpenAI (AI-Powered Features)

We use OpenAI's API to provide word definitions, contextual explanations, and AI-powered language learning features. When you use these features, the text of your query (word, phrase, or sentence) is sent to OpenAI for processing. OpenAI does not use API inputs to train their models. For more information, see the OpenAI Privacy Policy.

3.3 DeepL (Translation)

We use the DeepL API to provide high-quality sentence and subtitle translations. Text submitted for translation is sent to DeepL's servers for processing. For more information, see the DeepL Privacy Policy.

3.4 Apple Speech Framework (Speech Recognition)

We use Apple's built-in Speech Recognition framework for the shadow reading feature. Speech processing occurs on-device and is governed by Apple's privacy practices. We request microphone and speech recognition permissions before using this feature. For more information, see Apple's Privacy Policy.

3.5 YouTube API Services

The Service accesses video content and subtitle data through YouTube's API Services. By using the Service, you are also bound by Google's Privacy Policy. We do not host or store YouTube video content on our servers. Videos are streamed directly from YouTube's platform.

3.6 Google Sign-In

If you choose to sign in with Google, the authentication process is handled by Google's OAuth 2.0 service. We receive only the profile information you authorize (typically name, email, and profile photo). We do not access your Google contacts, files, or any other Google account data.

3.7 Apple In-App Purchase

Subscription payments are processed entirely by Apple through the App Store. We do not collect or store any payment card information. Apple's payment processing is subject to Apple's Privacy Policy.

4. Data Sharing and Disclosure

Lingdow does not sell, rent, trade, or otherwise share your personal data with third-party companies for their marketing or advertising purposes. We may share your information only in the following circumstances:

  • Service Providers: We share information with third-party service providers who perform services on our behalf, as described in Section 3 above (Supabase, OpenAI, DeepL). These providers are contractually obligated to use your information only to provide services to us and to protect your data consistent with this Privacy Policy.
  • Legal Requirements: We may disclose your information if required to do so by law, court order, subpoena, or other legal process, or if we believe in good faith that such disclosure is necessary to comply with applicable law, protect our rights or property, or protect the safety of our users or the public.
  • Business Transfers: In the event of a merger, acquisition, reorganization, bankruptcy, or sale of all or a portion of our assets, your information may be transferred as part of that transaction. We will notify you via email or prominent notice within the app before your information becomes subject to a different privacy policy.
  • With Your Consent: We may share your information for any other purpose with your explicit consent.

5. AI and Data Processing

Lingdow uses AI services (OpenAI and DeepL) for translation, word lookup, contextual explanations, and content summarization. Important details about our AI data practices:

  • We do not use your personal data to train AI models.
  • Content processed by AI services is used solely to provide you with real-time language learning features.
  • We do not combine AI query data with your personal identity for profiling or advertising purposes.
  • AI-generated translations, definitions, and explanations may contain inaccuracies and should be used as learning aids, not as authoritative references.
  • Our AI service providers (OpenAI) have committed not to use API inputs to train their models.

6. Data Security

We implement appropriate technical and organizational measures to protect your personal information against unauthorized access, alteration, disclosure, or destruction. These measures include:

  • Encryption of data in transit using TLS/SSL
  • Encryption of sensitive data at rest
  • Secure authentication mechanisms with hashed passwords
  • Regular security assessments and updates
  • Access controls limiting employee access to personal data
  • Use of secure, reputable cloud infrastructure providers

However, no method of transmission over the Internet or method of electronic storage is 100% secure. While we strive to use commercially acceptable means to protect your personal information, we cannot guarantee its absolute security. If we become aware of a security breach that affects your personal information, we will notify you in accordance with applicable law.

7. Data Retention

We retain your personal information for as long as your account is active or as needed to provide you with the Service. Specifically:

  • Account Data: Retained for the lifetime of your account. Upon account deletion, your account data is permanently deleted within 30 days.
  • Learning Data: Your saved words, sentences, watch history, and learning progress are retained while your account is active and deleted when you delete your account.
  • Speech Data: Voice recordings are processed on-device in real time and are not stored or retained by us.
  • AI Query Data: Text sent to AI services for translation or lookup is processed in real time and is not persistently stored by us.
  • Support Communications: Records of your communications with our support team may be retained for up to 2 years to help us improve our support services.
  • Aggregated and Anonymized Data: We may retain aggregated, anonymized, or de-identified data that can no longer be associated with you for analytical purposes indefinitely.

You may request deletion of your account and all associated personal data at any time through the app settings or by contacting us at help@lingdow.cn.

8. Your Rights

Depending on your location, you may have certain rights regarding your personal information. These rights may include:

  • Right of Access: You have the right to request a copy of the personal data we hold about you.
  • Right to Rectification: You have the right to request that we correct inaccurate or incomplete personal data.
  • Right to Erasure: You have the right to request that we delete your personal data, subject to certain exceptions (such as data we are legally required to retain).
  • Right to Restrict Processing: You have the right to request that we restrict the processing of your personal data under certain circumstances.
  • Right to Data Portability: You have the right to receive your personal data in a structured, commonly used, and machine-readable format and to transmit it to another controller.
  • Right to Object: You have the right to object to the processing of your personal data for certain purposes, including direct marketing.
  • Right to Withdraw Consent: Where we rely on your consent to process your personal data, you have the right to withdraw that consent at any time.

To exercise any of these rights, please contact us at help@lingdow.cn. We will respond to your request within 30 days. We may ask you to verify your identity before processing your request.

9. European Economic Area (EEA) and UK Users - GDPR

If you are located in the European Economic Area (EEA) or the United Kingdom, you have additional rights under the General Data Protection Regulation (GDPR) and the UK GDPR, respectively.

Legal Basis for Processing

We process your personal data on the following legal bases:

  • Performance of a Contract: Processing necessary to provide you with the Service (e.g., account creation, delivering language learning features, managing subscriptions).
  • Legitimate Interests: Processing necessary for our legitimate interests, such as improving the Service, ensuring security, and conducting analytics, provided these interests are not overridden by your data protection rights.
  • Consent: Processing based on your consent, such as when you opt in to speech recognition features. You may withdraw consent at any time.
  • Legal Obligation: Processing necessary to comply with applicable laws and regulations.

Data Protection Officer

For GDPR-related inquiries, you may contact us at help@lingdow.cn. You also have the right to lodge a complaint with your local data protection supervisory authority.

10. California Residents - CCPA / CPRA

If you are a California resident, you have additional rights under the California Consumer Privacy Act (CCPA), as amended by the California Privacy Rights Act (CPRA):

  • Right to Know: You have the right to request that we disclose the categories and specific pieces of personal information we have collected about you, the categories of sources from which the information was collected, the business purpose for collecting the information, and the categories of third parties with whom we share the information.
  • Right to Delete: You have the right to request that we delete your personal information, subject to certain exceptions.
  • Right to Correct: You have the right to request that we correct inaccurate personal information.
  • Right to Opt Out of Sale or Sharing: We do not sell your personal information. We do not share your personal information for cross-context behavioral advertising purposes.
  • Right to Non-Discrimination: We will not discriminate against you for exercising any of your CCPA rights.

To exercise your rights under the CCPA, please contact us at help@lingdow.cn. We will verify your identity before processing your request and respond within 45 days.

Categories of Personal Information Collected: In the preceding 12 months, we have collected the following categories of personal information: identifiers (email address, device identifiers), internet or other electronic network activity information (usage data, watch history), and inferences drawn from the above (language proficiency level, learning preferences).

11. International Data Transfers

Lingdow is based in China. Your information may be transferred to, stored, and processed in countries other than your country of residence, including China, the United States, and other countries where our service providers operate. These countries may have data protection laws that differ from those in your jurisdiction.

When we transfer personal data internationally, we take appropriate safeguards to ensure that your information receives an adequate level of protection, including:

  • Using service providers that comply with applicable data protection frameworks
  • Implementing contractual safeguards such as standard contractual clauses
  • Ensuring technical security measures are in place for all data transfers

By using the Service, you acknowledge and consent to the transfer of your information to countries outside your country of residence.

12. Cookies and Tracking Technologies

The Lingdow mobile app does not use browser cookies. However, we may use the following technologies:

  • Device Identifiers:We use Apple's Identifier for Vendors (IDFV) to identify your device for analytics and account security purposes. We do not use the Advertising Identifier (IDFA) and do not track you across other apps or websites.
  • Local Storage: We store your preferences, cached content, and authentication tokens locally on your device to improve app performance and user experience.
  • Analytics: We may collect anonymized, aggregated usage statistics to understand how the Service is used and to improve it. This data cannot be used to identify you personally.

We do not participate in ad networks. We do not use tracking technologies for targeted advertising. We do not display advertisements in the app.

13. Children's Privacy

The Service is not directed to children under the age of 13 (or the applicable age of consent in your jurisdiction, such as 16 in the European Economic Area). We do not knowingly collect personal information from children under these ages. If you are a parent or guardian and believe that your child has provided us with personal information, please contact us at help@lingdow.cn. If we discover that we have inadvertently collected personal information from a child under the applicable age of consent, we will take steps to delete that information as promptly as possible.

In compliance with the Children's Online Privacy Protection Act (COPPA), we do not knowingly collect, use, or disclose personal information from children under 13 residing in the United States.

14. Do Not Track Signals

Some web browsers transmit "Do Not Track" (DNT) signals. As the Lingdow Service is a mobile application and does not track users across third-party websites, DNT signals are not applicable. We do not track our users across third-party websites or apps for advertising purposes.

15. Third-Party Links

The Service may contain links to third-party websites or services, such as YouTube videos. We are not responsible for the privacy practices or content of these third-party services. We encourage you to review the privacy policies of any third-party services you access through the Service.

16. Changes to This Policy

We may update this Privacy Policy from time to time to reflect changes in our practices, technologies, legal requirements, or other factors. We will notify you of any material changes by:

  • Posting the updated policy within the app
  • Updating the "Last updated" date at the top of this policy
  • Sending you an email notification for significant changes

Your continued use of the Service after the effective date of any changes constitutes your acceptance of the updated policy. If you do not agree with the revised policy, you should discontinue use of the Service and delete your account.

17. Data Breach Notification

In the event of a data breach that is likely to result in a risk to your rights and freedoms, we will notify you without undue delay via email or prominent notice within the app. We will also notify relevant supervisory authorities as required by applicable law.

18. Contact Us

If you have any questions, concerns, or requests regarding this Privacy Policy or our data practices, please contact us at:

Lingdow
Email: help@lingdow.cn

For data protection inquiries, account deletion requests, or to exercise your privacy rights, please email us at help@lingdow.cn with the subject line "Privacy Request". We will respond to all legitimate requests within 30 days.