Privacy Policy
Effective date: May 20, 2026
Langu (“we”, “our”, or “us”) is a real-time language learning chat application. This Privacy Policy explains what personal data we collect, why we collect it, how we use and share it, and the choices you have. By using Langu you agree to these practices.
1. Who we are
Langu is operated by Alexandre Marques Kaio, registered in Brazil under MEI/CNPJ. Our primary contact for privacy matters is privacy@langu.app.
2. Information we collect
We collect the following categories of personal data:
Account and identity
- Phone number — required to create an account and verify your identity via one-time password (OTP).
- Display name — chosen by you during onboarding or in settings.
- Profile picture — optional image you upload; stored on Amazon Web Services (AWS) S3.
- About text — an optional short bio visible to your contacts.
Contacts
With your permission, Langu reads the phone numbers stored in your device's contacts list and sends them to our servers to identify which of your contacts also use Langu. We do not store your full contact list. We store only the phone numbers of contacts who are Langu users so we can show them to you as suggested connections.
Messages and chat content
All messages you send and receive through Langu are stored on our servers to provide the chat service, enable message delivery to recipients who are temporarily offline, and support real-time translation. Messages are retained for up to one month after they are sent, after which they are permanently deleted from our servers. A copy may remain on your device in local storage (SQLite) until you uninstall the app or delete the chat.
Language settings and fluency data
We store your chosen interface language, your fluent language, and fluency signal data (e.g. messages read and written per day) to provide the fluency tracking and progress features. This data is retained as long as your account exists.
Device and push notification token
We collect your device's Expo push notification token to send you message notifications. This token is associated with your account and updated each time you log in. You can disable notifications at any time in your device settings.
Billing and subscription data
If you purchase a Plus or Pro subscription or a boost pack, we record your subscription tier, purchase date, expiry date, and usage quotas. Payment processing is handled entirely by Stripe or the Apple App Store / Google Play — we do not store your card number, bank details, or any payment instrument data.
Usage and technical data
Our servers automatically log standard technical information when you use the app, including IP address, device platform (iOS or Android), and timestamps of API requests. This data is used for security, fraud prevention, and debugging.
3. How we use your information
| Purpose | Data used | Legal basis |
|---|---|---|
| Provide and deliver the chat service | Phone number, messages, contacts, device token | Contract performance |
| Translate messages in real time | Message text (sent to Google Cloud Translation) | Contract performance |
| Generate grammar explanations | Message text (sent to OpenAI) | Contract performance |
| Generate conversation suggestions (Plus/Pro) | Recent message context — up to 20 messages (sent to OpenAI) | Contract performance |
| Send push notifications | Device push token, message metadata | Contract performance |
| Process payments and manage subscriptions | Subscription tier, purchase records | Contract performance |
| Provide fluency tracking and progress reports | Fluency signals (read/write activity) | Contract performance |
| Prevent fraud, abuse, and enforce limits | Phone number, IP address, device info | Legitimate interest |
| Improve the service and debug issues | Technical logs, error data | Legitimate interest |
| Comply with legal obligations | Any data required by applicable law | Legal obligation |
4. Third-party services that process your data
Langu uses the following third-party services. By using Langu, you acknowledge that relevant portions of your data are processed by these providers under their own privacy policies.
5. International data transfers
Our primary servers are located in Brazil (AWS São Paulo). When you use translation or AI features, your message content is transferred to Google (USA) and OpenAI (USA) to process your request. Push notifications are routed through Expo's servers in the USA. These transfers are necessary to provide the core functionality of the service. Where required by applicable law, we rely on standard contractual clauses or equivalent mechanisms to protect your data during international transfers.
6. Data retention
| Data category | Retention period |
|---|---|
| Chat messages (server copy) | Up to 1 month after sending, then permanently deleted |
| Chat messages (device copy) | Until you uninstall the app or delete the chat |
| Account data (phone number, profile) | Until you request account deletion |
| Contacts matched in Langu | Until you request deletion or remove them |
| Fluency and language data | Until you request account deletion |
| Billing and subscription records | Until you request deletion (may be retained longer for legal/tax obligations) |
| Push notification token | Until you log out or request deletion |
| Server access logs | Up to 90 days |
7. Your rights
Depending on where you live, you have the following rights regarding your personal data:
- Access — request a copy of the personal data we hold about you.
- Correction — ask us to correct inaccurate data. You can update your display name, about text, and profile picture directly in the app.
- Deletion — request that we delete your account and associated personal data. To do so, email privacy@langu.app with subject “Delete my account”. We will process your request within 30 days.
- Data portability — request an export of the personal data you provided to us.
- Objection / restriction — object to or ask us to restrict certain processing activities.
- Withdraw consent — where processing is based on consent, you may withdraw it at any time without affecting the lawfulness of prior processing.
To exercise any of these rights, contact us at privacy@langu.app. We will respond within 30 days. We may ask you to verify your identity before processing your request.
If you are located in Brazil, you have additional rights under the Lei Geral de Proteção de Dados (LGPD), including the right to lodge a complaint with the Autoridade Nacional de Proteção de Dados (ANPD).
8. Children's privacy
Langu is intended for users who are 13 years of age or older. We do not knowingly collect personal data from children under 13. If you are a parent or guardian and believe your child under 13 has created a Langu account, please contact us at privacy@langu.app and we will delete the account promptly.
For users between 13 and 18 in Brazil, we rely on LGPD Article 14 guidance and require that a parent or guardian review this policy. School and institutional plans that involve users under 18 must be established by the responsible institution, which accepts liability for appropriate consent on behalf of their users.
9. Security
We use industry-standard security measures including HTTPS/TLS for all data in transit, encrypted storage for authentication tokens on your device (via secure enclave storage), and access controls on our servers. No system is completely secure — if you discover a security vulnerability, please report it to privacy@langu.app.
10. Cookies and tracking
The Langu mobile app does not use advertising trackers, behavioral analytics SDKs, or third-party cookies. Our website (langu.app) does not currently use analytics cookies.
11. Changes to this policy
We may update this Privacy Policy from time to time. When we make material changes, we will notify you by updating the effective date at the top of this page and, where required by law, by sending you a notification through the app or by email. Continued use of Langu after changes are posted constitutes your acceptance of the updated policy.
12. Contact us
For any privacy-related questions, requests, or complaints, contact us at:
Langu — PrivacyAlexandre Marques Kaio
Brazil
privacy@langu.app