Privacy Policy

CloudEx Inc. ("we", "us", or "our") operates the "Sentence Flashcards" app (the "Service"). This Privacy Policy explains what information the Service handles, where that information goes, and the choices available to you. By using the Service, you are deemed to have agreed to the practices described in this Policy.

1. Our Core Principle

Sentence Flashcards helps you learn words together with the sentences they are used in. It takes example sentences and their translations from Tatoeba (tatoeba.org), a free, open collection written by volunteers, and lets you study them with spaced-repetition flashcards, cloze exercises, listening practice, and more. You can also add sentences of your own. Your sentences and your study records are stored on your device, and we never view, collect, upload, or transmit them to our servers. There is no account and no sign-in, and the app contains no analytics or advertising SDK. Specifically, we do not have access to any of the following:

  • The sentences and translations you add or write, or your notes, tags, favorites, and decks
  • Your review history, streaks, and statistics
  • The sentences you have chosen not to see again
  • Your settings, such as the languages you study

The app connects to outside services only for the purposes described in Sections 2 and 3: getting sentences from Tatoeba, downloading translation data, opening a dictionary or search when you tap one, and the crash reporting and Google Play services described below.

2. Sentences, Translation, and Dictionaries

  • Getting sentences from Tatoeba: When you add new sentences, search Tatoeba for a word, or choose languages (the app shows how many sentences are available for each pair) — and, if "Add new sentences automatically" is on, when the app tops up new sentences as you open it — the app requests sentences from Tatoeba's public API (api.tatoeba.org). The request contains only search conditions: the language codes of the language you study and of your own language, the difficulty level, the word you search for, and filters such as "Native speakers' sentences only". It is sent with a User-Agent that contains the app's name and version and the address of our website. No account, device identifier, or sentence from your collection is sent. As with any web request, Tatoeba receives your device's IP address as part of the connection. Tatoeba's own terms and privacy policy apply to it.
  • Sentence authors and licenses: Sentences from Tatoeba are licensed under CC BY 2.0 FR (some under CC0). To credit their authors, the app stores each sentence's Tatoeba number, its owner (the Tatoeba user who added it), and its license together with the sentence, and shows them on the sentence screen. Tapping "Open on Tatoeba" opens that sentence's page on tatoeba.org in your browser.
  • On-device translation (translation drafts): Translation drafts for your own sentences use Google ML Kit Translation. Only when you tap "Draft translation", or download a language under "Translation data", does the app download a translation model (about 30 MB per language) from Google. The text is then translated on your device and is never sent to Google or to us. When the translation feature is used, ML Kit may send Google basic technical information about how the feature performs (such as the device model, OS version, and app version); this does not include the text you translate.
  • Dictionaries and search: When you tap a word in a sentence and choose "Look it up", the app lists dictionaries and search tools. The word is sent only when you tap one of them. Web dictionaries and searches — such as Google Translate, Weblio, Eijiro on the Web (ALC), Cambridge Dictionary, Merriam-Webster, Oxford Learner's Dictionaries, Naver, Youdao, Jisho, Wiktionary, and Google image and web search — open in your browser with the word in the address, and a dictionary or translation app on your phone that you choose receives the word directly. These sites and apps are not operated by us, and their own privacy policies apply.
  • Reading aloud: Sentences are read aloud by the text-to-speech engine on your device. The app does not send the text anywhere itself; the speech engine selected in your device settings is provided by its own developer and is subject to that developer's terms.

3. Information We Collect

3.1 Information Collected Automatically

  • Crash reports: Via Firebase Crashlytics. When the app crashes, we receive the stack trace, device model, OS version, app version, and a Crashlytics installation identifier (a random ID created for the app on your device, used to count how many users a crash affects). Crash reports do not include your sentences, translations, notes, or study records.
  • Purchase information: Premium is a one-time purchase made through Google Play Billing. Payment is completed on Google Play, and your payment details are handled by Google. The app receives from Google Play only whether Premium has been purchased. We never receive your credit card number or other payment details.
  • List of our other apps: To introduce our other apps, the app downloads a public list of them (names, short descriptions, and images) from a static site hosted on Cloudflare Pages. The request contains no personal data. As with any web request, the server receives your device's IP address as part of the connection. Tapping an app in the list opens its page on Google Play.

3.2 Information You Send Us

  • Email: When you email us, we receive your email address and whatever you write. If you use "Contact us" in the app, your email app opens with the app version, Android version, and device model filled in to help us look into your question; you can edit or delete them before sending. We use this only to reply to you.

3.3 Information Stored Only on Your Device

  • Your sentences and study data: Sentences, translations, readings, key words, notes, tags, favorites, decks, review history, and the list of sentences you have chosen not to see again are stored in a database inside the app on your device.
  • App settings: The languages you study, how new sentences are picked, and your review, reading-aloud, reminder, display, and app lock settings, as well as whether Premium is unlocked, are stored on your device.
  • Android backup: If backup is turned on in your device settings, Android may include the app's database and settings in the backup it saves to your own Google account, and may copy them to a new phone when you transfer your data. This is handled by Android according to your device's backup settings; we cannot access it.
  • Backups and exports you make: A manual backup (a JSON file), a CSV export, and Anki and PDF exports are written only to the location you choose. If you turn on automatic backup, the app saves a copy once a day to the folder you pick, keeping the last 7 days. Restoring a backup or importing a CSV file reads only the file you choose. If you save a file to a cloud service such as Google Drive, that service keeps it.
  • Notifications: Review reminders and the sentence of the day are scheduled on your device. No server is involved.
  • App lock: App lock uses Android's own fingerprint, face, or screen-lock prompt. The check is performed by Android, and the app learns only whether it succeeded. The app never receives your biometric data or your screen-lock PIN, pattern, or password.
  • Hiding the app from screenshots: You can turn on "Hide from screenshots and recents" in the settings so that the app's screens cannot be captured in screenshots and their contents are hidden in the recent-apps view.

3.4 Information We Explicitly Do Not Collect

  • Your name, email address, phone number, or contacts (the app has no account or sign-in; we receive your email address only if you email us)
  • The sentences, translations, notes, and study records in the app
  • Your location
  • Your device's advertising ID
  • The contents of your screen or of other apps

3.5 Permissions the App Requests and Their Purposes

  • Internet (INTERNET) and network state (ACCESS_NETWORK_STATE) — Used to get sentences from Tatoeba, download translation data, send crash reports, connect to Google Play for purchases, in-app reviews, and in-app updates, download the list of our other apps, and show this privacy policy in the app. The network state tells the app whether you are online and whether the connection is metered, so that it can ask before downloading translation data. Reviewing the sentences already in the app does not require an internet connection.
  • Notifications (POST_NOTIFICATIONS, Android 13+) — Shows review reminders and the sentence of the day. You can use the app without allowing notifications.
  • Run at startup (RECEIVE_BOOT_COMPLETED) — Schedules your reminders again after your phone restarts or the app is updated.
  • Biometrics (USE_BIOMETRIC / USE_FINGERPRINT) — Used only when you turn on app lock (Premium), to show Android's fingerprint, face, or screen-lock prompt.
  • Google Play billing (com.android.vending.BILLING) — Used for the one-time Premium purchase.

4. How We Use Information

The limited information we receive is used only for the following purposes:

  • Operating and maintaining the Service
  • Verifying your Premium purchase
  • Diagnosing and fixing crashes
  • Responding to support inquiries
  • Complying with applicable laws

5. Third-Party Services

Sentence Flashcards uses the following third-party services. Each service has its own privacy policy.

  • Tatoeba (tatoeba.org) — example sentences and their translations; receives only the search conditions described in Section 2
  • Google ML Kit Translation (Google LLC) — on-device translation; translation models are downloaded from Google
  • Firebase Crashlytics (Google LLC) — crash diagnostic data
  • Google Play Billing (Google LLC) — the one-time Premium purchase; payment is completed on Google Play
  • Google Play In-App Review and In-App Updates (Google LLC) — let you rate the app and install updates without leaving it; handled by Google Play
  • Cloudflare Pages (Cloudflare, Inc.) — hosts the static list of our other apps
  • Dictionaries and search sites — only those you choose to open (Section 2)

Sentence Flashcards does not use Google Analytics for Firebase or any other analytics service, contains no advertising SDK, and does not share your data with advertising networks. We do not sell your personal information.

6. Data Retention

  • Crash reports: retained by Firebase Crashlytics for 90 days, then deleted.
  • Emails you send us: kept only as long as needed to respond to you and to handle any follow-up.
  • Your sentences, study records, and settings on your device: kept until you delete them, use "Delete all sentences", clear the app's data, or uninstall the app.
  • Backup and export files you create: kept where you saved them until you delete them. Android backups in your Google account are managed by Google according to your account and device settings.

7. International Data Transfers

We are based in Japan. The services described above — crash diagnostics, Google Play, translation model downloads, Tatoeba, and the hosting of the list of our other apps — may operate infrastructure in various countries. When you use the Service, the minimal information described above may be processed outside your country of residence under standard contractual safeguards.

8. Your Rights and Choices

Depending on where you reside (e.g., the EEA, UK, California, Japan), you may have the right to request access to, correction of, or deletion of the limited information we hold. You can also:

  • Delete individual sentences at any time, or use Settings → Backup → "Delete all sentences" to delete all sentences, decks, review history, and hidden sentences from your device (display settings and your purchase are kept)
  • Uninstall the app or clear its data to erase everything stored inside the app on your device (backup and export files you saved elsewhere remain until you delete them)
  • Turn backup on or off in your device's backup settings
  • Turn off notifications, or withdraw the notification permission, in your device settings at any time
  • Contact us at the address below to make a request regarding the information we hold

9. Children's Privacy

We do not knowingly collect personal information from children under the age of 13 (or the minimum age applicable in your region). If we learn that we have received such information — for example, in an email sent to us — we will delete it promptly.

10. Changes to This Policy

This Privacy Policy may be updated from time to time. The latest version is always published at this URL together with its effective date. We will also notify you within the app of significant changes as appropriate.

11. Contact

For questions about privacy, data requests, or to report concerns, please email us at .

CloudEx Inc. (Japan)

Effective Date: November 10, 2026