Privacy Policy

Langlang (“Langlang,” “we,” “us”) is a language-learning app for iPhone and Android, and this is the privacy policy for the app and for langlang.app. It explains what we collect, why we collect it, and the choices you have. The short version: we collect what the app needs to teach you a language, and nothing else.

Information we collect

Account information. When you create an account we collect your name, email address, and a password. Passwords are hashed by our authentication provider; we never see or store them in plain text. You can also use Langlang with an anonymous session, in which case no name or email is collected until you choose to sign up.

Practice activity. To run your lessons and keep your progress in sync across devices, we store your language pair, your difficulty level (CEFR band), the phrases you have seen, the translations you submit, the grades and points you earn, and your streaks.

Voice conversations. The Voice feature streams your microphone audio in real time so a conversation partner can hear and answer you. Audio is processed to run the conversation. The app declares a camera entitlement only because the underlying real-time communication framework requires it — Langlang never captures or records video.

Purchases. Subscriptions are billed by Apple through the App Store. We receive a signed transaction record so we can activate your subscription; we never see your card number or billing address.

On your device. Preferences and practice caches are stored locally on your device, and your sign-in tokens are kept in the operating system’s secure storage. If you enable notifications, we store a push token so we can deliver them.

Diagnostics. The app and this website keep a diagnostic log on your device. When either hits a critical error, such as a crash, it automatically sends us that error and the diagnostic records just before it, which never include what you write or say in your lessons. The rest of the log leaves your device only if you export it and send it to us yourself.

Product analytics. We use PostHog to measure website visits, contact clicks, app opens, screen names, account creation, completed practice answers and confirmed purchases. Campaign tags on website visits tell us which advertising brought people here. App and server events use a pseudonymous account ID; signing up links earlier anonymous practice to that account. Analytics never includes lesson text, submitted translations, microphone audio, passwords, card numbers or billing addresses. We do not record sessions or screen contents.

How we use your information

• To provide the service: pick phrases at your level, grade your answers, run Voice conversations, and sync your progress.
• To generate feedback: your submissions and voice audio are sent to AI service providers solely to produce the grades, explanations, and conversation replies you see in the app.
• To manage your subscription and verify purchases.
• To send notifications you have opted into, such as practice reminders.
• To fix problems and keep the service secure.
• To understand which features people use and whether our advertising leads to signups and purchases.

We do not sell your personal information, and we do not use it for third-party advertising.

Who we share it with

• Convex, which hosts our backend, authentication, and database.
• OpenAI and ElevenLabs, which process practice submissions or voice audio to generate feedback, transcription, speech, and conversation.
• Cloudflare R2, which stores cached generated audio.
• Resend, which delivers account email.
• Apple, which processes App Store payments under its own privacy policy.
• Push notification services, if you enable notifications.
• PostHog, which processes the product analytics described above.
• Authorities, if the law genuinely requires it.

Data retention and deletion

We keep your data while your account is active. Delete your account — or write to us at 06max.zhang@gmail.com — and we will delete your profile and practice data, except records we are legally required to keep (such as purchase records). Anonymous session data that is never attached to an account may be removed as part of routine cleanup.

Security

All traffic between the app and our servers is encrypted in transit. Sign-in tokens live in your device’s secure storage, and access to production data is restricted.

Children

Langlang is not directed at children under 13, and we do not knowingly collect personal information from them. If you believe a child has given us personal information, contact us and we will delete it.

International transfers

Our primary backend is located in the United States. Service providers may process information in other locations under their own terms.

Your rights

Depending on where you live, you may have the right to access, correct, export, or delete your personal information, and to object to certain processing. Email 06max.zhang@gmail.com and we will respond to your request.

Changes to this policy

If we change this policy, we will post the new version here and update the effective date above.

Contact

Questions about privacy? Write to 06max.zhang@gmail.com. See also our Terms of Service.