Privacy Policy

Inku is a Japanese learning app for iPhone and the web. This policy explains what information we collect, how we use it, and the choices you have. We try to keep it short and plain.

If something here is unclear, email us at app@inkujapanese.com and we will explain.

The short version

• Learning data in the iPhone app and public browser tools stays on that device or in that browser.
• The signed-in web app stores your account and web learning data in a dedicated Cloudflare D1 database.
• We do not sell your data.
• We do not run ads.
• Web Pro uses Stripe for payments and RevenueCat for subscription access. Depending on the purchase link, checkout opens on inkujapanese.com or on RevenueCat's hosted page. You can buy as a guest or with a verified web account. Web and iPhone accounts, progress, and Pro entitlements stay separate.
• Google Analytics runs on public marketing pages when Do Not Track is off. It is excluded from private /app and /account pages.
• When the website or web app hits an error, Sentry receives a scrubbed technical report without your account, email address, or learning content.
• You can export your web learning data or delete your web account from the account screen.

Information stored on your device

The iPhone app and public browser learning tools save learning data locally using the storage provided by your phone or browser. This may include:

• Which characters, words, and phrases you have reviewed.
• How you answered each review (remembered or did not remember).
• Your streak, daily ink drops, and overall progress.
• Your onboarding answers (level, goals, pace) and the plan we built from them.
• Any cards or phrases you flag as broken.

This local learning data does not leave your device unless you choose to export, share, restore, or otherwise send it. Inku supports manual backup files; anyone with a backup file may be able to read or import its contents, so keep it private.

Android system backup and device transfer are disabled for Inku. On Apple devices, the operating system may include app data in a device or iCloud backup according to your settings and Apple's policies.

Information stored for your web account

The private web app at /app uses an account so your web learning progress can be restored in another browser. We store:

• Your email address and a hashed password. We never store your password in plain text.
• Your profile name, time zone, onboarding answers, and study preferences.
• Your answers, spaced-repetition schedule, custom words, saved items, lesson activity, progress, and session history.

Better Auth handles email-and-password authentication. After sign-in, your browser stores an HttpOnly, Secure, SameSite=Lax session cookie for up to 30 days. Signing out ends the current session.

Cloudflare Email Service sends account verification and password-reset messages from hello@accounts.inkujapanese.com. Creating an account does not subscribe you to marketing email.

Study and Pro emails

When you create a web account, or later in Settings, you can tick a box to get study emails. The box starts unticked, and the web app works the same either way.

If you opt in, you get a short series over your first two weeks: one email a day for the first three days, then one every two days, nine in all. They cover what is due for review, your streak and progress, how reviews work, and Inku Pro, using your saved learning progress. If you subscribe to Pro, the series stops and you get one Welcome to Pro email instead. Cloudflare Email Service sends them, and they contain no tracking pixels.

Every email has a one-click unsubscribe link, and Settings has an on/off switch. Either takes effect at once. Account and billing emails still arrive.

We store your choice with its time, where you made it and the version of the checkbox wording, your place in the email series or Pro list, and a record of each email sent. Deleting your account deletes these records.

Information we receive

Subscription status

If you subscribe to Inku Pro on iPhone, we receive purchase and entitlement information needed to unlock Pro features there. Apple handles In-App Purchase and RevenueCat helps us manage subscription status. We do not receive your full payment-card details.

RevenueCat records a customer country from the store transaction or, when that is unavailable, from the country associated with the customer's last-seen IP address. RevenueCat says it drops the raw IP address after determining the country.

Web Pro uses Stripe for payments and RevenueCat for subscription access. Depending on the purchase link, checkout opens on inkujapanese.com or on RevenueCat's hosted page. RevenueCat receives an app-generated guest or account identifier and purchase information to manage Web Pro access. Stripe receives the payment information you enter at checkout; we do not receive your full payment-card details. A guest purchase can be linked to a verified web account. Web and iPhone subscriptions remain separate.

Optional product analytics

In the native app, if you opt in, PostHog receives limited app-interaction events, app version information, and a random installation identifier. We use this to understand which parts of Inku are useful and where people get stuck. We do not send your learning answers, notes, email address, or advertising identifiers. You can turn analytics off in Settings.

Crash and diagnostic information

In the native app, Sentry receives crash reports and technical diagnostics so we can find and fix problems. This reporting is enabled by default and can be turned off in Settings. Reports may include:

• Device model and operating-system version.
• App version.
• Scrubbed error type, operation category, stack and debug information, release identifiers, and related technical context.

We do not set a Sentry user identity or attach your learning content to these reports.

On the website and the web app, Sentry receives an error report when a page, our server, or a scheduled job fails. Nothing is sent unless an error occurs. A report contains:

• The error type and message, the stack trace, and the website version.
• The page address or server route without its query string, and your browser's user-agent string.

Before a report leaves your browser or our server, we remove email addresses, cookies, authorization headers, access tokens, and query strings, which can hold sign-in, unsubscribe, purchase, or referral codes. We do not attach your account, email address, IP address, or learning content such as answers and custom words. There is no setting to turn off website error reports.

Feedback emails

If you use the in-app “Flag” feature or email app@inkujapanese.com, we see whatever you type, plus the email address you send from.

We do not request GPS or precise location, contacts, photos, microphone audio, browsing history, or content outside Inku. Services reached over the internet necessarily receive network information such as an IP address, which can sometimes imply an approximate area.

Website analytics

Public marketing pages use Google Analytics 4 to measure page visits and actions such as App Store and study-in-browser link clicks. We do not send email addresses or other direct identifiers in analytics events. The analytics script does not load when your browser sends a Do Not Track signal, and it is excluded from private /app and /account pages.

Android beta and launch waitlist

If you join the Android waitlist, we store your email address, signup time, and the version of your consent in a separate Cloudflare D1 table. Beta signups receive an invitation when Android testing is ready. Earlier launch-only signups remain launch-only unless you join the beta list yourself. Joining does not subscribe you to weekly email tips or create an Inku account.

We keep your entry until we send the beta invitation or launch notification you requested, or you ask us to remove it. To leave the list, email app@inkujapanese.com. We do not include your email in website analytics.

Optional email tips

The free kana chart page includes an optional email form. The chart is available without signing up. The form reports success only after a configured provider confirms that your address was stored. We record the email address, the page and form placement, campaign attribution, the consent time and version, delivery state, and a deduplication key.

No email provider is enabled by default. Before enabling one, we will name the processor and retention period here. You can unsubscribe from any tip email or ask us to delete your address at app@inkujapanese.com.

Partner referrals

Inku runs a partner program in which creators earn a commission on web purchases from people they refer.

• Referral cookie. When you open a partner's referral link or enter a partner code, your browser stores a first-party, HttpOnly, Secure cookie holding that partner's code and the time. It lasts 30 days and is never set just by visiting Inku. If you create an account or buy on the web while it is valid, we record which partner referred you, when, and under which version of the program terms.
• Click counting. To count unique clicks on a partner's link, we combine your IP address and browser name with a random value that changes every day and keep only the resulting one-way hash. We never store the IP address or browser name. The daily values and hashes are deleted after 2 days; Cloudflare D1 Time Travel backups can hold them for up to 30 days.
• Payments from referred customers. For a referred customer, we record the amount, currency, tax and refunds of each web payment, received from RevenueCat, to calculate commission.
• Partners. If you apply, we store your display name, the places you share, what you tell us about your audience, your full name, country and payout email for Wise, the terms version you accepted, and our decision. These payout details are visible only to you and Inku. We never see your bank details. We keep records of commissions and payouts.
• What partners see. Partners see totals only: clicks, sign-ups, paying customers and earnings. They never see who you are, your email, or your learning activity.

If you delete your account, your referral and payment records stay, without your account, because we need them to pay and account for commissions. A partner who deletes their account has their application details removed; their payout email and name are kept only while money is still owed to them.

How we use this information

We use the information we collect to:

• Create, secure, and recover your web account.
• Save, restore, and export your web learning progress.
• Measure whether a change to the app is helping people learn.
• Diagnose and fix bugs.
• Keep your iPhone and web Inku Pro subscriptions in the right state.
• Respond when you email us.
• Measure which website pages lead to App Store or browser-app interest.
• Send optional Japanese tips when you explicitly subscribe.
• Credit partners for referrals and pay their commission.

We do not use your data to train AI models. We do not build a behavioral profile of you. We do not share your data with advertisers.

Third-party services

Inku uses a small number of third-party services. Here is what each one sees:

Apple App Store

If you install Inku from the App Store, Apple receives information about the download. If you buy iPhone Pro, Apple processes the In-App Purchase and receives the billing information.

RevenueCat (subscription management)

RevenueCat receives a signal when you subscribe, renew, or cancel an iPhone subscription so Inku can unlock Pro features there. RevenueCat does not receive your full card information from Apple In-App Purchase. It receives an app-generated customer identifier, purchase information from Apple, and a customer country determined as described above.

For current Web Pro purchases, Stripe handles payment fields on inkujapanese.com or through RevenueCat's hosted checkout. RevenueCat manages subscription status using an app-generated guest or account identifier and purchase information. Stripe processes payments, receives the checkout billing information, and provides the customer portal. Web Pro does not unlock iPhone Pro. Previous web subscriptions stay with their original billing provider.

Wise (partner payouts)

If you are a partner, Wise receives your full name, payout email and the amount of each payout. Wise emails you a link to add your bank details, which Wise collects and holds under its own privacy policy.

PostHog (optional product analytics)

PostHog receives the limited app-interaction data described above only when you opt in. You can withdraw that choice in Settings.

Sentry (crash and error reporting)

Sentry receives crash reports and technical error information from the native app, the website, and the web app. We use them to find and fix problems. You can opt out in the native app's Settings. Website and web-app reports are scrubbed as described above and carry no account identity.

ElevenLabs (voice audio)

We use ElevenLabs to pre-record Japanese pronunciation files before release for the native app. The web app does not send your learning activity to ElevenLabs or request ElevenLabs speech on demand.

Where available, the web app can use your browser's optional Japanese speech-synthesis feature and a voice installed on your browser or device.

Google Analytics (website measurement)

Google Analytics receives limited public marketing-page visit and action data when Do Not Track is not enabled. We use it to understand which pages help people find Inku and which App Store or study-in-browser links are used. We do not send email addresses in analytics events, and Google Analytics is excluded from private /app and /account pages.

Cloudflare (website, web app, account email, and storage)

Cloudflare Workers hosts the website and web app through OpenNext. A dedicated Cloudflare D1 database stores the web account and learning data described above. Cloudflare Email Service delivers account verification and password-reset messages, and the optional study emails. Cloudflare processes the requests and data needed to provide these services under its service settings and published policies.

AI providers (future features)

If we ship an AI-powered feature later (for example, a conversational practice partner or speech feedback), we may send the text or audio you produce to a third-party AI service. We will only send what is needed for the feature to work, and we will update this policy before the feature ships so you know exactly what is involved.

Where your data is stored

Native learning data and public browser-tool data are stored locally on your phone or in your browser. Copies may also exist in manual backups you create or in an operating-system backup under the platform provider's control.

Your web account and web learning data are stored in Cloudflare D1. Account email is delivered through Cloudflare Email Service. Native crash and diagnostic reports, and scrubbed website and web-app error reports, flow to Sentry. Optional native app-interaction events flow to PostHog only after you opt in. Native subscription information flows to RevenueCat and Apple; current web subscription information flows to RevenueCat and Stripe. Public marketing-page measurement can flow to Google Analytics when Do Not Track is not enabled.

These providers may process information in countries other than the one where you live. Their privacy policies describe their locations, safeguards, and retention practices.

How long we keep your data

• Local learning data: until you clear it, remove the app or browser data, or replace it by importing a backup. Exported backups remain wherever you saved or shared them.
• Web account and learning data: including our checkout attempts and retry payloads, until you delete your web account, subject to the backup window described below.
• Study email choice and send records: until you delete your web account.
• Web sessions: the browser session cookie lasts for up to 30 days and is ended when you sign out.
• Subscription records: Apple, RevenueCat, Stripe, and providers of previous web subscriptions, including RevenueCat Web Billing, retain their own records according to their policies, contracts, legal obligations, and configured settings.
• Analytics and diagnostics: native analytics and diagnostics, and website and web-app error reports, are retained according to the settings and policies of PostHog and Sentry.
• Optional email tips: no provider is enabled by default. We will publish the processor and retention period before enabling capture.

Cloudflare D1 Time Travel is an automatic backup and restore system. It can retain recoverable database history for up to 30 days on the Workers Paid plan or 7 days on the Workers Free plan. Deleted rows may remain in that history until the applicable window ages out. Time Travel restores overwrite the database in place, so our restore procedure reapplies the deletion ledger described below before restoring service.

How to delete your data

You can download an export of your web learning data from your account screen. You can also delete your web account there after confirming your password and a recent session. Deletion removes the account and its owned profile, progress, answers, custom words, saved items, lesson activity, and history through database relationships.

After deletion, we retain only an opaque account identifier and the deletion time in a deletion ledger. We use that ledger to prevent an account or its data from being recreated if a database backup is restored. Deleted rows may remain recoverable in D1 Time Travel until its applicable 30-day or 7-day history window expires, but they are not available through your account or the app.

For the native app and public browser tools, use Inku's local data controls where available or clear the app or browser storage. Removing an app normally removes its local data, subject to operating-system backups and any manual backup files you created.

In the native app, analytics can be disabled and diagnostic reporting can be opted out in Settings. Website and web-app error reports have no setting. Because we do not attach your account identity to these records, we may not be able to locate a particular anonymous event. You can still email app@inkujapanese.com and we will help with any information we can reasonably identify.

If you subscribed to email tips, use the unsubscribe link in any email or contact app@inkujapanese.com to ask us to delete the address.

Deleting a web account does not cancel an iPhone or web subscription. Cancel iPhone subscriptions through Apple, current Web Pro through the Stripe customer portal, and previous web subscriptions through their original billing provider. See our Terms of Service.

Security

Every network request the app makes is sent over HTTPS. Web passwords are stored as hashes, never as plain text. Web sessions use HttpOnly, Secure, SameSite=Lax cookies. Diagnostic data and native subscription signals are encrypted in transit.

No system is perfect. If we discover a security incident that affects information we hold, we will investigate and provide any notice required by applicable law.

Children's privacy

Inku is not directed at children under 13. We do not knowingly collect information from children under 13. If you believe a child is using the app, email app@inkujapanese.com and we will help.

Users between 13 and the age of majority in their country should have a parent or guardian review this policy first.

Your rights

Depending on where you live, you may have the right to:

• Access the data we hold about you.
• Correct it.
• Delete it.
• Object to certain processing.

You can access and export your web learning data or delete your web account from its account screen. Local native and public browser-tool data remains under your control on your device. For anonymous diagnostic data held through our providers, email app@inkujapanese.com and we will help.

Changes to this policy

If we change this policy in a way that affects you, we will update the date at the top and provide an appropriate notice in the app, on this website, or through the relevant app store. Small editorial edits (typos, clearer phrasing) do not trigger a notice.

Contact us

Questions about this policy or your data:

app@inkujapanese.com

Inku is operated by Bao Hua, a sole proprietor based at 903 8 Ave SW, Calgary, AB T2P 0P7, Canada.