Privacy Policy
App: Kioku Developer: Soylu Digital Solutions (SODISOL), based in Turkey Effective date: September 26, 2026 Last updated: October 14, 2026 Contact: admin@sodisol.com Support: https://kioku.sodisol.com/en/support
1. Who We Are
Kioku is a spaced-repetition study app for iPhone, iPad, Mac, and Apple Watch. This policy describes how data is handled when you use the app and the Kioku website. Soylu Digital Solutions (SODISOL), based in Turkey, operates Kioku.
2. Data in the Kioku App
Study data and sync
Decks, cards, chapters, and review history are stored on your device. Premium users may enable iCloud Sync in the app. If enabled, study data is stored and synced through Apple's CloudKit using the iCloud account configured on your device. Apple processes this data under its own terms and privacy policy. Sync depends on Apple's services, your account, and available iCloud storage.
The iPhone app can exchange decks, study progress, and related settings directly with its paired Apple Watch using Apple's WatchConnectivity framework. Study data therefore travels between the paired devices; Watch use does not mean that data remains only on the Watch.
Preferences and notifications
App preferences, including appearance, language, and notification choices, are stored on your device. Daily reminders are available in the free app. Premium also includes optional due-card alerts. Notifications are scheduled through Apple's notification services and require your permission.
Word Forms and Catalog
Word Forms uses data bundled with Kioku and works offline in English, German, Turkish, and Japanese. Kioku includes free Catalog theme decks (Colours and Animals) in four languages and Premium ready-made courses (A1.1 and A1.2 in English, German, and Turkish, and JLPT N5 in Japanese). Learn mode lets you re-read chapters without affecting your reviews. JSON study-data import and export are available to Free and Premium users.
Subscription management
Kioku configures RevenueCat at launch to check subscription entitlements. It may begin with an anonymous RevenueCat app user ID. If an iCloud user record ID is available, Kioku may ask RevenueCat to associate the subscription with that ID so entitlements can be recognized across devices. RevenueCat processes information under its privacy policy. Purchases and payment processing are handled through Apple's App Store; SODISOL does not receive your full payment details through Kioku.
Under Settings → Privacy & Data Requests, the app shows a "Subscription Customer ID". To request access to or deletion of subscription records held by RevenueCat, email admin@sodisol.com with that ID; the app offers a prefilled email for this. For a deletion request, SODISOL asks RevenueCat to delete the customer record. This does not cancel an App Store subscription; cancel it in your Apple account's subscription settings. Apple's own transaction records are retained by Apple under its terms. If the subscription stays active and you keep using the app, a new customer record may be created to check access.
Kioku has no AI features. Word Forms is bundled and does not require an AI service. Kioku contains no analytics or advertising.
3. Data on the Kioku Website
The website stores your selected language and theme in your browser's localStorage until you clear the site's data. It is self-hosted on a server in Aachen, Germany. To deliver a page, the server processes request data such as your IP address, requested path, date and time, response status, and browser or referrer information sent with the request. Nginx produces access-log output, which the operator discards and does not retain. You do not need an account to view the site. If you email admin@sodisol.com, we receive your email address and the information in your message so we can respond. Email to admin@sodisol.com is handled by Proton Mail, operated by Proton AG in Switzerland, which processes it under its privacy policy.
4. Delete Study Data, Export, and Retention
You can export study data as a JSON file from Settings. The app's Delete Study Data action requires two confirmations. It removes decks, cards, chapters, and review history from this device, cancels due-card alerts, refreshes the widget data, and queues a reset sync for the paired Watch. The Watch copy is cleared when it receives that sync; if the Watch is offline or unavailable, its copy may remain until then. The app checks for study data in iCloud and requests its removal if present. Cloud deletion remains pending until removal is confirmed, and can be retried if iCloud is unavailable. Preferences and subscription data are kept by this action.
Canceling a subscription is a separate action and does not delete study data. Deleting or reinstalling the app does not itself confirm that data stored in iCloud has been deleted. Use Delete Study Data while the app can access iCloud to request removal from both local and cloud study stores.
On-device study data remains until you delete it in the app. CloudKit data remains until Apple processes the deletion request; a paired Watch copy remains until it receives the queued reset. App preferences remain on the device until changed or removed; website language and theme remain in localStorage until you clear them. Website access-log output is discarded and is not retained by the operator. Support emails and records of privacy requests are kept for up to five years after the last message, then deleted. Apple and RevenueCat retain service and transaction data under their own service terms, for as long as needed to provide the service or meet legal requirements. RevenueCat's current published DPA says customer data is retained through the service agreement and, after it ends, is returned or destroyed on the customer's request made within 30 days, subject to standard backup and archive practices. The RevenueCat Data Processing Agreement is incorporated into RevenueCat's Terms of Service (Section 4.2) and applies to Kioku.
5. How Data Is Used and Shared
We use study data and app settings to provide the study features you choose; CloudKit and WatchConnectivity move data between devices when you use those features; and RevenueCat receives an app user ID (initially potentially anonymous, and possibly an iCloud user record name), subscription status and related App Store transaction information, and technical app or device information to check and manage subscription access. Apple provides CloudKit, the App Store, WatchConnectivity, and notifications. Study data is also sent directly between your iPhone and paired Watch. RevenueCat and Apple process information under their own service terms and privacy policies. SODISOL does not receive full payment-card details through Kioku. We do not use study data for advertising.
International processing
Apple says that personal data may be transferred to or accessed by Apple entities worldwide; its policy describes Standard Contractual Clauses for transfers of data about people in the EEA, UK, and Switzerland. RevenueCat's published privacy policy says its end-user data is stored on AWS in the United States. RevenueCat's DPA, which applies to Kioku, provides EU Standard Contractual Clauses for restricted transfers. Emails are processed by Proton Mail (Proton AG, Switzerland) under its privacy policy; Switzerland has an EU adequacy decision. See Apple's Privacy Policy, iCloud terms, RevenueCat's Privacy Policy, and RevenueCat's DPA.
6. Your Choices and Rights
You can export or delete study data in the app, turn off optional iCloud Sync, manage notification permissions in device settings, and clear website localStorage through your browser. Turning off sync stops future syncing but does not by itself delete data already in iCloud.
We respond to data-subject requests within one month of receipt, as set out in GDPR Article 12(3). For complex requests, we may extend this by two further months and will notify you of the extension. The in-app JSON export provides your study data in a machine-readable format. SODISOL cannot read your iCloud private database, so study data held in iCloud is accessed or deleted through the app or through Apple's iCloud settings.
Where the GDPR applies, we rely on Article 6(1)(b) to provide the app and features you request, including optional sync and subscription access; Article 6(1)(f) to deliver the website and respond to general support enquiries or maintain the service; and Article 6(1)(a) where a processing activity is based on consent, which we explain when asking for it. We use website localStorage to remember language and theme choices you make. You may request access to, correction or deletion of your personal data, restriction of processing, and portability where the legal conditions are met; object to processing based on legitimate interests; and withdraw consent where processing relies on it. You may complain to a data protection supervisory authority, including the authority where you live, work, or believe an infringement occurred. In Turkey, you may also exercise applicable rights under the Personal Data Protection Law (Law No. 6698) through the relevant process. To make a request or ask a question, email admin@sodisol.com. We may need information sufficient to understand and respond to your request.
7. Children
Kioku is a general-purpose study app. Parents or guardians should supervise a child's use where required by local law. If you believe personal information about a child has been sent to us, contact admin@sodisol.com.
8. Changes
We may update this policy as the app or applicable requirements change. The revised date above identifies the latest version. Material changes may also be communicated in the app where appropriate.
9. Contact
Soylu Digital Solutions (SODISOL), based in Turkey Email: admin@sodisol.com Support: https://kioku.sodisol.com/en/support