Privacy Policy

Last updated: 6 October 2026

Katsu: JLPT Quiz & Kanji, also referred to as Katsu and previously distributed as JLPT Quiz: Kanji & Vocabulary, is provided by VIODRA STUDIOS BILISIM HIZMETLERI SANAYI VE TICARET LIMITED SIRKETI (“VIODRA STUDIOS”, “we”, “us”). We are based in İstanbul, Türkiye and are the controller of personal data processed for the purposes described in this policy.

This policy covers the Katsu Android and iOS applications and the supporting services used for accounts, purchases, learning-content delivery, feedback and backups. Features and processing can differ by platform, app version, region and the choices you make. Earlier Android versions may not include all of the features described here.

Contact: support@viodrastudios.com
Postal address: İcadiye Mahallesi, Cemil Meriç Sokak, Girne Apt. Blok No: 87/5, Üsküdar, 34674 İstanbul, Türkiye.

This policy explains data use. Reading it or accepting our Terms of Use does not, by itself, give consent to optional tracking or other processing that requires separate consent.

1. The information involved

Learning records and preferences

Katsu stores learning information on your device, including favorites, question progress, quiz answers and results, study history, achievements, activity dates, game progress, Kanji TV progress and learning preferences. It also stores settings such as language, appearance, pronunciation preferences and notification choices.

These records support the features you use and are primarily stored on your device. Copies can leave your device through cloud backup or file sharing, and selected usage statistics can be sent through Analytics, as described below.

When you update from a supported earlier Android version or restore an earlier backup, Katsu may read and convert existing learning and profile records so that your progress can continue. Some older records are retained locally for compatibility and can be included in a learning backup.

Guest sessions and sign-in

You can start learning without signing in with Google or Apple. When a network connection and the authentication service are available, Katsu can create a Firebase anonymous account with a technical user identifier for the guest session. “Anonymous” here describes an account without a chosen sign-in provider; it does not mean that the authentication service processes no technical data.

If you choose Google or Apple sign-in, Firebase Authentication and the chosen provider process the information needed to authenticate you. Katsu can receive your account identifier, provider information, name, email address and profile-photo URL, depending on what the provider supplies and what you authorize. Apple may supply a private relay email address. A name supplied during Apple sign-in may be saved with the Firebase account so it remains available on later visits.

Authentication services also process connection and security information, such as IP addresses, device or browser information and authentication tokens. We do not receive your Google or Apple password.

Linking a provider can associate your current guest progress with your signed-in account. Signing into an existing account can merge the relevant on-device records. This does not automatically move a purchase between stores or make all devices share the same learning database.

Your profile name and photo

You may choose a local display name and select a profile image through your device’s photo picker. Katsu stores the resulting profile image and name on the device for the active learning profile. A photo supplied by your sign-in provider may also be displayed; loading it can contact that provider’s image service.

Your local profile name and image may be included in a cloud backup or exported backup file. They are not restricted to the original device once you use those features. Changing your local Katsu profile does not change the name or photo on your Google or Apple account.

Purchases and Pro access

Apple or Google processes purchases and payment details. Katsu uses RevenueCat to verify purchases, determine Pro access, support restoration and understand purchase activity. This involves a RevenueCat-generated customer identifier, store transaction or receipt information, product and subscription details, purchase and expiry dates, and entitlement status. We do not receive your full payment-card details.

Purchase verification uses customer and transaction identifiers managed by RevenueCat and the relevant store. Purchase records are managed separately from your Katsu learning account. These identifiers can relate to a customer or installation even when no name or email address is provided.

Some paid listening packages are downloaded from our content-delivery service. To authorize a download, the app sends its RevenueCat customer identifier, platform and requested package information to that service, which checks the relevant entitlement with RevenueCat. The delivery service also processes ordinary connection information and uses limited access tokens and rate limits to protect downloads.

Content reports and support

When you submit an in-app content report, we receive a report identifier, submission time, app version and platform, the reported content and its reference, the selected language, the reason for the report and any description you enter. An audio-related report can include a reference to the relevant learning-audio file.

Please avoid entering personal or sensitive information in the optional description. Our hosting provider receives connection information, including the IP address associated with a request, to operate and protect the service. The reporting service uses an IP-derived value for abuse prevention.

Unsent report drafts can remain on your device so you can resume or retry them. Reports are sent when you choose to submit or retry them. Submitted reports are stored in our reporting service and reviewed by authorized personnel.

The separate Help & Support feature opens an email draft in your mail application. It can include your message, app and device details, operating-system version, language, theme, time, Pro status and a recent technical activity summary. You can review or edit the draft before sending it. If you send it, we receive your email address and the message and attachments you choose to send.

Analytics, diagnostics and configuration

Katsu uses Google Analytics for Firebase to understand feature use and improve the app. Events can describe screen visits, quiz starts and results, selected study types and levels, counts and scores, feature interactions, purchase-flow outcomes, backup operations and error outcomes. The Analytics service can also process installation or app-instance identifiers, app and device information, session information and approximate geographic information.

Analytics events and technical identifiers can be personal data even when they do not contain your name or email address.

Firebase also supports remote configuration and technical services. Depending on the platform and enabled SDK behavior, technical processing can include installation identifiers, messaging registration information, native crash reports and related device or application diagnostics. The app includes Firebase Crashlytics and Firebase Cloud Messaging components in addition to Authentication, Analytics and Remote Config.

Advertising choices and Apple’s tracking permission do not necessarily disable every Analytics, diagnostic or service operation. The current app does not provide a separate Analytics on/off switch. Section 8 explains the available controls and how to contact us about your data.

Advertising information

The free version can display ads through Google AdMob, including banner, full-screen and optional rewarded ads. The advertising SDK and the partners involved in an ad request may process IP addresses, approximate location inferred from them, advertising or other permitted device identifiers, app/device information, ad impressions and interactions, and diagnostic information. These data support ad delivery, measurement, personalization where permitted, security and fraud prevention.

The data and partners involved depend on your platform, region, privacy choices and the advertising configuration. Where a privacy form is shown, it provides information about the purposes and participating partners. See Google’s information about data use in partner apps.

Katsu does not request precise GPS location for its learning features. IP-based approximate location is different from GPS access.

2. Cloud backups and portable files

Cloud backup is an optional feature. On Android, Katsu uses a restricted application-data area in the Google Drive account you authorize. On iOS, it uses the Katsu area of iCloud Drive, associated with the Apple account configured for iCloud on your device. The iCloud account is separate from the Google or Apple account used to sign into Katsu.

The app can also export and import portable backup files. On supported iOS versions, you can explicitly authorize an import from an existing Google Drive backup.

Backups can contain learning records, profile overrides including the selected image, preferences and identifiers used to preserve the origin of existing records. They do not serve as a copy of your store purchase entitlement or your sign-in session.

Automatic cloud backup may be enabled during account or backup setup when the relevant cloud access is available. Check Settings → Auto Cloud Backup to review the current choice. Turning it off stops the app’s automatic backup activity; it does not erase files already stored in your cloud account. Automatic backup runs around app use and should not be understood as continuous, instant synchronization between devices.

New Katsu backup files use authenticated encryption, but they are portable and do not require a user-selected password or the original account to import. Someone who obtains a compatible backup file may be able to import and read its contents through Katsu. Keep exported files private and choose sharing destinations carefully. We do not describe this file format as a guarantee that only you can decrypt the data. Older imported backups may use a different format.

Google, Apple or a sharing destination you select processes the backup under its own service arrangements. Your operating system may also back up app data under your device-level backup settings.

3. Why we process information

We process information to provide study features, maintain accounts and profiles, preserve and restore progress, verify purchases, deliver eligible content, respond to reports and support requests, provide ads where applicable, improve the app, protect services from misuse and meet legal obligations.

Where a legal basis is required, we rely on the basis appropriate to the activity:

Different advertising partners can act on the bases explained in the relevant privacy form and their notices. Consent can be withdrawn for future processing without affecting processing that was lawful before withdrawal. We do not treat acceptance of these documents as a substitute for consent required by law.

4. Who receives information

We share information needed for the purposes described in this policy with the following categories of recipients:

Some providers process data for us, while others also act independently for their own services. Their applicable terms and privacy notices explain those activities: Google, Firebase, Apple, RevenueCat and Cloudflare.

We may also disclose relevant information to professional advisers or competent authorities when necessary to comply with law, protect rights or address fraud and security incidents. A business transfer involving Katsu may involve relevant records, subject to applicable protections and any required notice.

Advertising disclosures involving identifiers or usage information can be considered a “sale”, “sharing” or targeted advertising under some privacy laws, even without a cash payment for the data. Applicable opt-out choices are described in section 8.

5. International processing

We operate from Türkiye and use providers with infrastructure in other countries, including the United States. Information may therefore be processed outside the country where you live.

Where applicable law restricts an international transfer, the transfer must rely on an appropriate lawful mechanism, such as a recognized adequacy framework or contractual safeguards that apply to the particular provider and transfer. Contact us for information about the safeguards relevant to your data. A provider’s participation in a framework does not mean that VIODRA STUDIOS itself holds that certification.

6. Retention

Retention depends on the data, the feature and the reason it is needed. Relevant criteria include whether an account or entitlement remains active, whether a support or content issue is unresolved, the need to protect services or handle disputes, applicable legal obligations and the provider’s retention and deletion arrangements.

Where identification is no longer necessary, we can retain non-identifying information such as a corrected learning entry or aggregate statistics. Contact us about a particular record rather than assuming that one deletion action covers all of these systems.

7. Account deletion and removing other copies

For a signed-in account, use Profile → Delete account and complete any required provider reauthentication. Once successfully completed, this process deletes the Firebase app account and the corresponding learning/profile records on the device performing the deletion. Apple authorization is revoked as part of the supported Apple-account deletion flow. Continuing to use Katsu as a guest can create a new technical guest account.

Account deletion does not automatically:

• Delete your Google or Apple account.
• Cancel a store subscription, refund a purchase or erase store/RevenueCat transaction records.
• Remove Google Drive or iCloud backup files, exported files, copies on other devices or files already shared with someone else.
• Remove every previously submitted report, support message, Analytics event or provider diagnostic record.

To stop subscription renewal, use the subscription-management controls of the store that billed you. To remove cloud backups, delete the relevant Katsu files or app data through Google Drive or iCloud storage controls. Also remove any exported copies you no longer want. Disable automatic backup before removing copies if you do not want current local data to be backed up again.

If you cannot access the app, are using a guest session, or want help with other personal data, email support@viodrastudios.com with the subject “Katsu privacy or deletion request”. Tell us which account or record the request concerns and your platform. For a content report, include its reference if you have it, or enough non-sensitive context to help locate it. We may need proportionate verification because a report or technical identifier may not be linked to an email address. Do not send passwords or complete payment-card information.

8. Your choices and rights

Advertising preferences. Use the advertising-privacy entry under Settings when it is available. Google’s privacy system determines when that entry is required and which regional choices it displays. It can allow you to change consent or exercise applicable opt-out rights. If it is unavailable and you need help exercising a right, contact us.

iOS tracking. Apple’s App Tracking Transparency permission controls access to the advertising identifier and tracking covered by Apple’s rules. You can review it in the device’s privacy settings. Declining tracking does not block Katsu’s ordinary use. It does not automatically remove all ads, stop essential service processing, or grant Pro access.

Android advertising identifier. Your device may offer controls to reset or delete the advertising identifier or manage ad privacy. Availability and naming depend on the Android version.

Notifications. Practice reminders are scheduled locally on your device. You can turn them off in Katsu’s Settings or in your operating system’s notification settings. Permission to show reminders is separate from permission to track you.

Photos, files and audio. You choose images and files through system pickers and control applicable permissions in device settings. Katsu plays learning audio and uses the device’s text-to-speech service for pronunciation; it does not require recording your voice for these features. A selected text-to-speech engine may use its own network service and settings. Files or images you explicitly save or share are handled by the destination you select.

Depending on your location and the law that applies, you may have rights to obtain information or a copy, correct data, request deletion, restrict or object to processing, receive portable data, withdraw consent, or opt out of certain advertising uses. You can also complain to the relevant data-protection authority. Where applicable, we will handle authorized-agent requests and appeals, and will not unlawfully discriminate against you for exercising a privacy right.

For people in Türkiye, rights under Law No. 6698 include learning about processing and recipients, requesting correction or erasure where the conditions apply, requesting notification of those actions to recipients, objecting to adverse results based solely on automated analysis and seeking compensation for unlawful processing. Contact us using the details above; any legally required verification or application procedure still applies.

Katsu does not use quiz results to make automated decisions about employment, credit or other similarly significant legal matters. Automated study scoring and purchase-access checks are part of the app’s functionality.

9. Children’s privacy

Requirements for processing children’s personal data, including when parental or guardian consent is required, depend on applicable law. An app-store content rating does not replace those requirements.

If you believe a child’s personal data has been collected or used without legally required consent, or otherwise requires removal or another protective action, contact support@viodrastudios.com so we can investigate and take appropriate action.

10. Security

We use measures appropriate to the services involved, including encrypted network connections, access restrictions for report administration and validation of backup and download data. No device, network or storage system can be guaranteed completely secure.

Protect your device and connected accounts. Treat exported backup files as private even though their format uses encryption. A Pro purchase removes the in-app advertising covered by that entitlement; it is not a promise that all account, purchase, backup or technical processing stops.

11. Changes and contact

We may update this policy when the app, providers or applicable requirements change. The revised page will show its update date. We will provide additional notice or request new consent where required; a policy update does not retrospectively grant a missing consent.

For questions or requests, contact support@viodrastudios.com.