Kanjin Privacy Policy

This Privacy Policy explains how Kanjin LLC, a Wisconsin limited liability company based in the United States (“Kanjin,” “we,” “us,” or “our”), collects, uses, stores, shares, and protects information when you use Kanjin, including our website at kanjincafe.com, any Kanjin-operated subdomains, our web application, accounts, lessons, reviews, decks, subscriptions, contact forms, and related services.

By using Kanjin, you acknowledge this Privacy Policy.

Questions, privacy requests, refund requests, billing questions, support requests, or other requests may be sent to kanjincafe@gmail.com or submitted through the Contact Us form on kanjincafe.com.

1. Who Operates Kanjin

Kanjin is operated by Kanjin LLC, a Wisconsin limited liability company based in the United States.

Kanjin provides a Japanese learning service focused on kanji, radicals, vocabulary, readings, meanings, spaced repetition, review scheduling, mastery stages, decks, pathways, and related study tools.

2. Information We Collect

We collect information you provide directly, information generated through your use of Kanjin, and information processed through service providers that help us operate Kanjin.

The information we collect depends on how you use Kanjin, whether you create an account, whether you purchase a paid plan, whether you contact us, and which features you use.

3. Account Information

When you create or manage an account, we may collect:

• first and last name, which are required during account creation and may be changed in account settings but not fully removed while your account remains active;
• email address;
• date of birth, used for age eligibility and account compliance;
• password or authentication data;
• account settings;
• email preferences;
• time zone;
• subscription status;
• account creation date;
• account deletion or cancellation information;
• billing status or plan status, if applicable.

Authentication may be handled through Supabase or other authentication tools used by Kanjin.

4. Age Eligibility Information

Kanjin is not intended for children under 13.

Kanjin may ask for your birth month, day, and year during account creation to determine whether you are eligible to create an account.

If the age gate indicates that a user is under 13, Kanjin will not allow account creation.

For users who are eligible to create an account, Kanjin currently stores date of birth in the user account record. Kanjin uses this information to verify age eligibility, maintain eligibility records, support account compliance, and enforce age-related requirements in our Terms of Service.

Kanjin does not use date of birth information for advertising.

Kanjin may also store related age-gate records, such as whether the age gate was passed, the age gate version, the method used, and the date and time of confirmation.

5. Legal Consent and Policy Records

Kanjin may store records showing that you accepted, acknowledged, or agreed to certain legal terms, policies, or checkout disclosures.

These records may include:

• Terms of Service version;
• Privacy Policy version;
• Sources & Acknowledgments version, if applicable;
• age gate version;
• checkout disclosure version;
• refund policy version;
• document hashes or content hashes;
• acceptance or acknowledgment timestamps;
• acceptance method, such as checkbox or button click;
• acceptance context, such as signup, checkout, resubscription, policy update, or account settings;
• app domain;
• user account identifier;
• hashed IP address, if collected;
• hashed user agent, if collected.

Kanjin uses these records to document user consent, verify legal acceptance, resolve disputes, prevent abuse, maintain compliance records, and operate the service.

6. Study and Progress Information

Because Kanjin is a learning service, we collect study-related information needed to provide lessons, reviews, and progress tracking, including:

• lessons started or completed;
• review history;
• correct and incorrect answers;
• mastery stages;
• spaced repetition scheduling data;
• weak items;
• deck and pathway progress;
• selected decks and pathways;
• custom deck activity;
• item notes;
• user-added synonyms;
• settings such as daily lesson targets, automatic vocabulary, mastery-based progression, and advanced start;
• item detail activity and study statistics.

7. User Content

We may collect content you create, save, or submit in Kanjin, including:

• custom decks;
• notes;
• synonyms;
• feedback;
• bug reports;
• content reports;
• contact form submissions;
• support messages;
• other information you choose to submit.

Custom decks, notes, and synonyms are currently private. Kanjin does not currently offer public deck sharing, public profiles, public study statistics, leaderboards, comments, following, or other public-sharing features.

If Kanjin later offers public-sharing or community features, we may update this Privacy Policy and our Terms of Service, and additional rules may apply.

Do not include sensitive personal information in notes, custom decks, synonyms, support messages, feedback, reports, or other User Content unless necessary.

8. Payment and Subscription Information

Kanjin uses Stripe to process payments and manage subscriptions. Kanjin does not store your full payment card number.

We may receive and store limited payment-related information from Stripe, such as:

• subscription status;
• plan type;
• billing email;
• Stripe customer ID;
• Stripe checkout session ID;
• Stripe subscription ID;
• payment status;
• renewal status;
• cancellation status;
• invoice or receipt information;
• limited transaction metadata;
• tax-related information where applicable;
• refund status, if applicable.

Your payment information is processed by Stripe according to Stripe’s own terms and privacy policy.

9. Pre-Signup Checkout Information

Kanjin may allow you to purchase a paid plan before creating or completing an account.

If you purchase before signup, your paid access must be claimed by creating an account using the same email address used at checkout.

Kanjin may link paid access by matching the authenticated user’s email address with Stripe billing records associated with that same email address. If you create an account using a different email address than the one used at checkout, paid access may not attach automatically.

If you complete payment but cannot claim access, Kanjin may need to verify your payment, email address, Stripe checkout session, Stripe customer record, or other billing information before granting access or resolving the issue.

10. Contact, Support, and Email Information

If you contact Kanjin, use the Contact Us form, or email Kanjin directly, we may collect:

• name;
• email address;
• subject;
• message;
• page or context of submission;
• time of submission;
• user agent or technical metadata, if collected for security or debugging;
• related account information, if you are logged in;
• any other information you choose to include.

Kanjin uses Gmail’s SMTP relay through Nodemailer for contact messages, billing reminders, email-change confirmations, authentication messages, account messages, support messages, and other transactional emails.

Kanjin uses email primarily for transactional, account, authentication, billing, subscription, security, support, service, and policy-related communications. Kanjin does not currently send marketing or promotional emails.

If Kanjin later sends marketing or promotional emails, we will update our practices as needed and provide any required opt-out method.

11. Error Reports, Bug Reports, and Content Reports

Users may report errors, bugs, content issues, or support issues through Kanjin’s Error Report feature, the Contact Us form on kanjincafe.com, or direct email to kanjincafe@gmail.com.

Reports may relate to kanji, radicals, vocabulary, readings, meanings, example sentences, deck placement, pathway placement, study behavior, account issues, technical issues, billing issues, or other parts of Kanjin.

If you submit a report through the Error Report feature, Kanjin may collect the information you provide and related context needed to investigate the issue. This may include your message, report category, affected item or page, page path, action context, timestamps, account information, browser or device information, technical metadata, and a screenshot or visual snapshot of the page.

For reports submitted through the Error Report feature, Kanjin may automatically capture and store a screenshot or visual snapshot with the report. Screenshots may include visible page content, study content, account interface elements, user-entered information, or other information visible on your screen at the time the report is submitted.

Error report screenshots and action context may be stored in Kanjin’s database as part of the report record. Kanjin does not currently store these screenshots in a separate Supabase Storage bucket.

If you submit a report through the Contact Us form or direct email, Kanjin may collect the information included in your submission, along with related metadata such as your name, email address, subject, message, time of submission, and related account information if available.

Reports may be reviewed by Kanjin administrators or authorized personnel through internal admin tools. Kanjin may use internal validation, moderation, prioritization, or reputation signals to help evaluate reports, identify reliable reports, prevent abuse, and improve content quality.

Please avoid submitting reports from pages that display sensitive personal information unless necessary.

12. Technical, Device, and Usage Information

When you use Kanjin, we may collect technical and usage information, including:

• IP address;
• browser type;
• device type;
• operating system;
• pages viewed;
• referring pages;
• feature usage;
• approximate location based on IP address;
• log data;
• error information;
• performance data;
• analytics events.

Kanjin is built with TailwindCSS and Shadcn on the frontend, uses Supabase for database and authentication, Vercel for hosting and deployment, Stripe for payments, Gmail SMTP through Nodemailer for email delivery, and Vercel Web Analytics for usage analytics.

13. Vercel Web Analytics

Kanjin uses Vercel Web Analytics to understand aggregate usage, performance, and page activity.

We do not intentionally send email addresses, payment details, authentication tokens, private notes, private custom deck content, private synonyms, or other sensitive personal information to Vercel Analytics through custom events, URLs, or query parameters.

Some analytics data may include technical information such as page views, referrer information, device type, browser type, operating system, approximate geolocation, and performance-related information.

14. Cookies, Browser Storage, and Similar Technologies

Kanjin may use cookies, localStorage, sessionStorage, browser-based storage, and similar technologies to:

• keep you signed in;
• remember preferences;
• operate the service;
• secure your account;
• preserve app state;
• support signup and checkout flows;
• cache temporary app information;
• understand usage and performance;
• support analytics;
• improve the user experience.

Kanjin may use Supabase session cookies or related authentication storage to keep users signed in.

Kanjin may use localStorage for app state, such as study settings, “stay logged in” preferences, or similar user-interface preferences.

Kanjin may use sessionStorage for temporary workflows, such as pending signup after checkout, error-report action context, chain-alignment cache, notification sandbox state, or similar temporary app state.

Kanjin may include install metadata for progressive web app support. Kanjin does not currently offer a full offline study mode. Study, review, synchronization, billing, account management, and core app functions may require a network connection.

Kanjin may scaffold or prepare browser database features, such as IndexedDB, for future local buffering or sync-related functionality. If Kanjin later enables offline review buffering, offline study, or expanded local database storage, we may update this Privacy Policy or provide additional notice where appropriate.

Information stored on your device may remain there until you clear browser storage, delete app data, sign out, or use account deletion tools. Clearing browser storage may affect login status, preferences, cached data, pending workflows, or app functionality.

We do not currently provide a separate Cookie Policy. If our use of cookies or tracking changes in a way that requires additional notice or consent, we may update this Privacy Policy or provide additional controls.

15. Do Not Track and Global Privacy Control

Some browsers or extensions may send “Do Not Track” signals or Global Privacy Control signals.

Kanjin does not currently sell personal information or share personal information for cross-context behavioral advertising. Kanjin also does not currently use third-party advertising cookies.

Because there is no uniform industry standard for responding to “Do Not Track” signals, Kanjin does not currently respond to Do Not Track signals.

Where required by applicable law, and if Kanjin’s data practices make such signals applicable, Kanjin will honor legally recognized opt-out preference signals, such as Global Privacy Control.

16. How We Use Information

We use information to:

• provide and operate Kanjin;
• create and manage accounts;
• authenticate users;
• verify age eligibility;
• record legal acceptance, policy acknowledgment, age gate confirmation, checkout disclosure acceptance, and refund policy acknowledgment;
• deliver lessons, reviews, decks, pathways, and study tools;
• track progress, mastery, and spaced repetition scheduling;
• save custom decks, notes, synonyms, and preferences;
• process subscriptions and billing through Stripe;
• link pre-signup checkout purchases to accounts;
• send transactional emails;
• respond to support requests;
• confirm email changes;
• send billing reminders;
• process refund requests;
• detect, prevent, and investigate abuse, fraud, security issues, and technical problems;
• debug errors and improve performance;
• review error reports, bug reports, content reports, and screenshots;
• analyze usage through Vercel Web Analytics;
• improve Kanjin’s content, features, and design;
• review feedback, bug reports, and content reports;
• comply with legal, tax, accounting, and regulatory obligations;
• enforce our Terms of Service.

17. How We Share Information

We do not sell your personal information.

We may share information with service providers that help us operate Kanjin, including:

• Supabase for database, storage, and authentication;
• Vercel for hosting, deployment, performance, and analytics;
• Stripe for payments, subscriptions, billing, taxes, and fraud prevention;
• Google/Gmail SMTP services used with Nodemailer for transactional email delivery;
• security, logging, monitoring, or infrastructure providers;
• professional advisors such as lawyers, accountants, or tax advisors, where needed.

We may also share information if we believe it is necessary to:

• comply with law or legal process;
• enforce our Terms of Service;
• protect Kanjin, our users, or others;
• investigate fraud, abuse, security issues, or technical problems;
• respond to lawful requests from public authorities;
• complete a merger, acquisition, financing, reorganization, sale of assets, or business transfer.

18. AI-Assisted and Manually Reviewed Content Workflows

Kanjin may use AI-assisted or automated tools internally to help evaluate the commonality, frequency, priority, or suitability of Japanese words, meanings, readings, examples, or learning content.

These tools may reference public, open, licensed, or third-party language resources such as dictionary data, kanji data, frequency information, example sentence datasets, textbook alignment information, or similar sources. Kanjin uses these tools to assist content preparation, not to create user profiles for advertising.

Kanjin manually reviews and edits learning items before publication to the best of our ability. We may use user feedback, reports, and study data to identify content that may need correction or improvement.

Kanjin does not use private user notes, private custom decks, or private synonyms to train public AI models unless we update this Privacy Policy and provide any required notice or consent.

19. Third-Party Language Resources

Kanjin may reference, incorporate, adapt, compare against, or derive information from public, open, licensed, or third-party Japanese language resources, including dictionary data, kanji data, kanji decomposition data, example sentence data, frequency or priority information, textbook alignment information, and other language-learning references.

Kanjin may use resources such as JMdict English common-word subset data, KANJIDIC2 data, KRADFILE data, Tatoeba Japanese-English sentence data, manually written contexts, generated context drafts, and curated internal rules reviewed for Kanjin.

Third-party resources, names, datasets, copyrights, trademarks, and licenses remain the property of their respective owners. Where required by applicable licenses, Kanjin will provide attribution, acknowledgments, license notices, or source information in the service, documentation, footer, Sources & Acknowledgments page, item detail pages, or another reasonable location.

20. User Content and Future Sharing

Custom decks, notes, and synonyms are currently private. Kanjin does not currently offer public deck sharing, public profiles, public study statistics, leaderboards, comments, following, or other public-sharing features.

If Kanjin later allows users to share or publish custom decks, profiles, statistics, leaderboards, comments, or other content, the content you choose to share may become visible to other users according to the sharing settings you select. Additional terms, notices, or privacy controls may apply.

Private study data, review history, account information, private notes, private custom decks, and private synonyms will not be made public simply because a sharing feature exists.

21. Data Retention

We retain personal information only for as long as reasonably necessary to provide Kanjin, maintain your account, operate subscriptions, preserve study progress, comply with legal, tax, accounting, and regulatory obligations, resolve disputes, prevent fraud or abuse, enforce our Terms, and maintain legitimate business records.

In general:

Account information is retained while your account is active.

Date of birth may be retained while your account is active and as reasonably necessary to verify eligibility, maintain compliance records, enforce age-related requirements, prevent abuse, resolve disputes, or comply with legal obligations.

Study progress, review history, mastery stages, decks, notes, synonyms, and settings are retained while your account is active unless deleted or de-identified.

Legal consent and policy records, such as Terms acceptance, Privacy Policy acknowledgment, age gate confirmation, checkout disclosure acceptance, refund policy acknowledgment, document versions, document hashes, timestamps, and related metadata, may be retained as needed to document consent, resolve disputes, comply with legal obligations, and enforce our Terms.

Billing, subscription, invoice, tax, and payment-related records may be retained as needed for tax, accounting, fraud-prevention, dispute-resolution, and legal compliance purposes.

Support messages, feedback, bug reports, content reports, error reports, screenshots, and contact form submissions may be retained as needed to respond to you, maintain support history, improve Kanjin, investigate issues, prevent abuse, and protect Kanjin or users.

Technical, analytics, and operational data may be retained as needed for security, debugging, performance, abuse prevention, analytics, and service operation.

Although Kanjin does not currently maintain a separate user-facing backup or export system, our service providers may maintain backups, logs, replicas, or retention systems according to their own infrastructure, security, and legal practices. Some information may remain in provider backups or logs for a limited period after deletion.

22. Account Deletion

You may start account deletion from Settings. For security, account deletion may require email verification and an in-app confirmation step.

When account deletion is confirmed, Kanjin will attempt to cancel any active Stripe subscription connected to your account and clear active billing fields from your Kanjin user record.

Account deletion may not be completed instantly. Some deletion steps may require additional processing or manual administrative review, including authentication cleanup, subscription verification, billing-record handling, fraud-prevention checks, or service-provider processing.

Deleting your Kanjin account may not delete historical billing, invoice, tax, payment, fraud-prevention, or transaction records maintained by Stripe or retained by Kanjin where reasonably necessary for legal, tax, accounting, dispute-resolution, or compliance purposes.

After account deletion, your account may not be recoverable.

Some retained records may not be visible in the app but may remain where necessary for the reasons described in this Privacy Policy.

23. Data Export

Kanjin does not currently offer a built-in export feature for study progress or custom decks.

You may contact us at kanjincafe@gmail.com or submit a request through the Contact Us form on kanjincafe.com with privacy-related requests. Depending on your location and applicable law, you may have rights to request access, correction, deletion, or a copy of certain personal information.

24. Privacy Rights

Depending on where you live, you may have rights regarding your personal information, such as the right to request access, correction, deletion, portability, restriction of certain processing, objection to certain processing, or withdrawal of consent where processing is based on consent.

To make a privacy request, contact Kanjin at kanjincafe@gmail.com or submit a request through the Contact Us form on kanjincafe.com. We may need to verify your identity before completing a request.

We will respond to privacy requests as required by applicable law.

25. EEA, UK, and Swiss Users

If you are located in the European Economic Area, the United Kingdom, or Switzerland, Kanjin LLC is the controller of your personal information.

We process personal information to provide Kanjin, perform our agreement with you, manage accounts and subscriptions, respond to support requests, protect Kanjin and users, comply with legal obligations, and improve the service. Depending on the context, our legal bases may include contract performance, legitimate interests, legal obligations, and consent where required.

Depending on your location, you may have rights to request access, correction, deletion, portability, restriction, objection to certain processing, or withdrawal of consent where processing is based on consent.

You may make a privacy request by contacting kanjincafe@gmail.com or by submitting a request through the Contact Us form on kanjincafe.com. We may need to verify your identity before completing a request.

26. California Privacy Notice

Kanjin does not currently sell personal information or share personal information for cross-context behavioral advertising. Kanjin also does not currently use third-party advertising cookies.

Depending on whether California privacy laws apply to Kanjin and your request, California residents may have rights to request access to personal information, deletion of personal information, correction of inaccurate personal information, information about how personal information is used or disclosed, and non-discrimination for exercising privacy rights.

To make a privacy request, contact Kanjin at kanjincafe@gmail.com or submit a request through the Contact Us form on kanjincafe.com. We may need to verify your identity before completing a request.

27. International Users

Kanjin is operated from the United States. If you access Kanjin from outside the United States, your information may be processed and stored in the United States or other countries where our service providers operate.

Data protection laws in those locations may differ from the laws in your location.

28. Security

We use reasonable administrative, technical, and organizational measures to protect information. However, no online service, database, transmission, or storage system can be guaranteed to be completely secure.

You are responsible for keeping your login credentials secure and for promptly notifying us if you believe your account has been accessed without permission.

29. Children’s Privacy

Kanjin is not intended for children under 13. We do not knowingly collect personal information from children under 13.

Kanjin may use an age gate during account creation to determine whether a user is eligible to create an account. If the age gate indicates that a user is under 13, Kanjin will not allow account creation.

If you believe a child under 13 has provided personal information to Kanjin, contact us at kanjincafe@gmail.com or through the Contact Us form on kanjincafe.com, and we will take appropriate steps to delete the information where required.

If you are under the age of majority in your location, you may use Kanjin only with the permission and supervision of a parent or legal guardian.

30. Third-Party Links and Services

Kanjin may link to or rely on third-party services, including Stripe and other infrastructure providers. This Privacy Policy does not control third-party websites, services, or policies.

We encourage you to review the privacy policies of third-party services you use.

31. Changes to This Privacy Policy

We may update this Privacy Policy from time to time. When we make material changes, we may notify you by email, in-app notice, or another reasonable method.

The updated Privacy Policy will be effective when posted unless a later effective date is stated. Your continued use of Kanjin after an updated Privacy Policy becomes effective means you acknowledge the updated Privacy Policy.

32. Contact

Questions or requests about this Privacy Policy may be sent to:

Kanjin LLC Email: kanjincafe@gmail.com

You may also submit privacy requests, refund requests, billing questions, support requests, or other requests through the Contact Us form on kanjincafe.com.