Folius Privacy Policy

Effective date: August 29, 2026

This Privacy Policy explains how Folius products and services, including the Folius Android application and the Folius Chrome Extension ("Folius", "we", "us", or "our"), process information when you use them. Folius is operated by KASSUS RECORDINGS LLC.

1. Information we collect

Depending on the features you choose to use, Folius may collect or process the following categories of information:

  • Email address and account identifier when you create or use a Folius account.
  • Authentication and session information used to sign you in and maintain your account.
  • Vocabulary and learning data, including saved words, meanings, translations, examples, learning status, quiz activity, practice results, corrections, and feedback.
  • Reading activity, including reading position, progress, bookmarks, and related app interactions.
  • Book and library metadata, such as title, author, identifiers, progress, and other information associated with books in your library.
  • User-generated language-learning content, including sentences, written answers, practice responses, transcripts, and conversation responses.
  • Optional voice or sound recordings when you use voice-practice or spoken-answer features.
  • Search and lookup information, such as words, sentences, or text submitted for dictionary or translation features.
  • Chrome Extension data, including text you intentionally select for translation, the selected source and target languages, Saved Words, local learning statistics, synchronization metadata, and account-session information when you choose to sign in.
  • Google Play subscription information, including purchase tokens, product information, subscription status, expiration time, Premium entitlement status, and Premium transfer history.
  • Technical information such as IP address, User-Agent, request timestamps, and similar information used for authentication, security, server operation, and abuse prevention.

2. Books and files

Imported book files are primarily processed and stored locally on your device. Folius does not normally upload the complete imported book file to our servers.

However, information about a book, such as its title, author, identifiers, reading progress, and related library metadata, may be synchronized with your Folius account.

When you actively use features such as AI explanations, grammar tools, translation, word-choice assistance, or book conversation features, selected text, sentences, or limited excerpts from a book may be sent from your device for processing.

3. AI and language-learning features

Folius provides optional AI-powered features, including explanations, grammar assistance, vocabulary practice, book conversation, feedback, and voice transcription.

When you use these features, relevant content may be sent through Folius servers to OpenAI for processing. Depending on the feature, this may include:

  • selected text or sentences;
  • book context or excerpts;
  • language-learning answers;
  • conversation responses;
  • practice history or feedback relevant to the requested feature;
  • optional voice recordings for transcription.

Folius does not intentionally include your email address or Folius account UUID in the content sent to OpenAI for these AI requests.

AI responses, corrections, transcripts, or feedback may later be stored as part of your Folius learning history if the relevant feature saves or synchronizes that information.

4. Translation and dictionary services

Some dictionary and translation features use external services.

Text submitted for translation may be sent to MyMemory, operated by Translated. Individual dictionary lookup words may be sent to DictionaryAPI.dev.

In the Folius Chrome Extension, translation is initiated when you intentionally select text on an ordinary web page. The extension sends the selected text and the relevant source and target language information to MyMemory so that the requested translation can be returned.

The Chrome Extension does not send the complete web page to MyMemory as part of this translation feature, and Folius does not use this access to collect your browsing history.

These services may process information according to their own privacy, retention, and service policies.

5. Voice recordings

Folius requests microphone access only for features that require spoken input.

If you choose to use a voice-practice or spoken-answer feature, your audio recording may be transmitted through our backend and sent to OpenAI for speech transcription and language-processing functionality.

Using voice features is optional.

6. Account and synchronization data

Folius uses Supabase for account authentication, account storage, and synchronization.

Signing in to the Folius Chrome Extension is optional. If you sign in, the extension uses the same Folius account and synchronization infrastructure as the Android application and may synchronize compatible Saved Words and related deletion metadata with your account.

If you choose to create and use a Folius account, synchronized information may include vocabulary, learning activity, grammar practice history, reading progress, bookmarks, library metadata, settings, achievements, and other app state associated with your account.

You may also use parts of Folius without creating an account. Account-based collection is therefore optional where guest use is available.

7. Chrome Extension

The Folius Chrome Extension runs a content script on ordinary HTTP and HTTPS web pages because its core function is to detect text that you intentionally select and display a translation popup next to that selection.

The extension is event-driven. It does not continuously scan page content, collect browsing history, or transmit entire pages to Folius or to the translation provider.

The extension stores certain information locally in Chrome, including translation-language preferences, Saved Words, local learning statistics, and synchronization or deletion metadata.

If you sign in, authentication access and refresh tokens are stored in Chrome extension session storage rather than persistent local storage. They are cleared when the Chrome browser session ends, and you may need to sign in again after restarting Chrome. Your Folius password is not stored by the extension after the sign-in request is completed.

When you delete a Saved Word, Folius may retain a limited deletion marker containing information such as the word, language direction, and deletion time. This marker is used to synchronize the deletion across devices and to prevent the deleted word from being restored during a later sync.

8. Google Play Billing and Premium

Premium subscriptions are purchased through Google Play.

Folius may receive and store information needed to verify and manage a subscription, including:

  • Google Play purchase token and a cryptographic hash of the token;
  • product and base-plan information;
  • subscription state;
  • expiration time;
  • Premium ownership and entitlement status;
  • Premium transfer events and related operational history.

Google Play handles payment credentials directly. Folius does not receive or store your credit card number, CVV, bank account number, or payment-card credentials.

9. How we use information

  • providing and operating Folius features;
  • account creation, authentication, synchronization, and account management;
  • reading progress and learning functionality;
  • personalized language-learning feedback and practice;
  • dictionary, translation, AI, and transcription functionality;
  • operating the Chrome Extension, including user-initiated selection translation, local Saved Words, and optional synchronization;
  • Premium subscription verification and entitlement management;
  • fraud prevention, security, abuse prevention, and enforcement of Premium transfer limits;
  • maintaining the reliability and security of our servers.

10. Service providers and third parties

Folius uses third-party services to provide certain functionality. These may include:

  • Supabase — account authentication, database hosting, and synchronization;
  • OpenAI — AI processing and speech transcription;
  • Google Play and Google Android Publisher services — subscription purchase and verification;
  • MyMemory / Translated — translation functionality;
  • DictionaryAPI.dev — dictionary lookups;
  • Google Fonts — web font delivery where applicable.

The information sent to a service depends on the feature you use. We do not sell user data or use Folius user data for third-party advertising.

11. Data retention

Account information and synchronized Folius data are generally retained while your Folius account remains active, unless you delete or replace specific information through normal app use.

When a Folius account is deleted, the account and synchronized reading and learning data associated with that account are deleted from the Folius account database.

Certain subscription and operational records may be retained after account deletion where necessary to preserve Google Play subscription entitlement, prevent abuse, enforce Premium transfer rules, maintain transaction integrity, or meet operational and legal requirements.

For example, a Premium subscription record and purchase token may remain after account deletion, while the deleted Folius user's ownership identifier is removed or set to null. Historical Premium transfer records may also remain with user identifiers removed.

Server, authentication, infrastructure, or third-party provider logs may also be retained according to the applicable system or provider retention settings.

Chrome Extension authentication tokens are session-scoped and are cleared when the Chrome browser session ends. Local extension preferences, Saved Words, learning statistics, and synchronization metadata may remain in the Chrome profile until removed through Folius, cleared from Chrome storage, or the extension is uninstalled, subject to Chrome's own storage behavior.

12. Account deletion

You may delete your Folius account from within the application.

You may also access the public account-deletion page here:

https://api.kassusrec.com/delete-account

Deleting your account removes your Folius authentication account and synchronized account data such as saved vocabulary, reading progress, bookmarks, learning history, and library metadata.

Some Premium subscription, security, operational, or historical records may remain as described in the Data Retention section above.

Deleting your Folius account does not necessarily erase imported book files or other local files that remain stored on your device.

13. Security

Folius uses HTTPS/TLS for its primary application network communications. We take reasonable measures to protect information transmitted between the app, our servers, and service providers.

No method of electronic transmission or storage can be guaranteed to be completely secure.

14. Changes to this Privacy Policy

We may update this Privacy Policy when Folius features, data practices, or service providers change.

When the policy is updated, the effective date at the top of this page will be changed.

15. Contact

Folius is operated by KASSUS RECORDINGS LLC.

For privacy questions or requests concerning Folius, you may contact us at:

kassusrec@gmail.com