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iCloud Sync is an optional Premium feature and needs no separate Kioku account. When enabled in Settings, Kioku stores and syncs study data using Apple's CloudKit service and your iCloud account. Apple's service terms and privacy practices apply.

Free use includes up to 5 decks with 20 cards each, spaced repetition study, Learn mode, the Apple Watch app, widgets, daily reminders, offline Word Forms, a furigana toggle, free Catalog theme decks (Colours and Animals) in four languages, JSON export and import, and Delete Study Data. Premium removes deck and card limits and adds ready-made courses, optional iCloud sync, and due-card alerts.

Premium includes ready-made A1.1 and A1.2 courses in English, German, and Turkish and a JLPT N5 course in Japanese. Together they hold nearly 4,000 dictionary-checked cards, and each card can be used with meanings in the other three languages. If you study with English meanings, the German, Turkish and Japanese courses give you about 2,900 cards. Premium also gives you unlimited decks and cards, iCloud Sync without an account, and due-card alerts.

Learn mode lets you re-read the chapters of a deck at any time without affecting your reviews. It does not change your ratings or your spaced repetition schedule.

Kioku runs on iPhone, iPad, Mac, and Apple Watch, and requires iOS 18.6, macOS 15.6, or watchOS 11.6 or later. The app is available in English, German, Japanese, and Turkish.

No. Kioku has no AI features. Word Forms uses bundled data and works offline.

No. Kioku has no analytics and no ads. RevenueCat is used only to manage subscriptions. See the Privacy Policy for details.

All billing is managed by Apple. You can cancel your subscription at any time by going to your device's Settings > [Your Name] > Subscriptions, and selecting Kioku. You will retain Premium access until the end of your current billing period.

Yes. Both Free and Premium users can import and export study data as JSON from Settings. Delete Study Data takes two confirmations. It removes study data from this device, cancels due-card alerts, refreshes widget data, and queues a reset sync for the paired Watch. The Watch copy clears when it receives that sync, so it may remain on an offline Watch until then. The app checks iCloud and requests removal of study data found there; cloud deletion remains pending until confirmed and can be retried if iCloud is unavailable. Preferences and subscription data are kept. Canceling a subscription is separate and does not delete study data.