Privacy Policy — Yukigo

Last updated: 21 October 2026

Data controller

YUKIGO LTD (trading as "Yukigo"), a company registered in England and Wales under number 17399318 Registered office: 71-75 Shelton Street, Covent Garden, London WC2H 9JQ, United Kingdom Registered with the Information Commissioner's Office (ICO) under number ZC229683 Contact: support@yukigo.app

In short

Yukigo is built local-first: your study data lives on your device and you can study offline. Your progress is also saved to an anonymous sync profile (a random identifier, with no name or email), so it doesn't get lost; linking an account is optional and lets you retrieve it on another device. When you ask Yuki (the AI tutor) a question, it is processed by our server to generate the answer. We show no ads and we never sell your data.

Data stored on your device

All study data (progress, reviews, streaks, statistics, settings) is stored locally on your phone. You can use the app without creating an account. So that it doesn't get lost, your study data is additionally synced to an anonymous profile hosted on our servers — see the next section.

Sync profile and optional account

So that your progress doesn't get lost, the app automatically creates an anonymous sync profile: a random identifier — with no name, email or anything else that identifies you — that your study progress is associated with: review/SRS state and the log of your review answers, XP and its daily log, JLPT exercises and exam simulations with the answers you gave, streak, level and JLPT level, daily goal, settings, the avatar you pick, your country (the one of your phone's region, unless you pick another one or none), a random identifier for each device and, if you set them, your display name and leaderboard participation. If the app has to recreate the anonymous profile (for example after losing the session), we record the link between the new profile and the old one, so that your progress isn't lost.

If you choose to link an account (via email, Apple or Google sign-in), for example to retrieve your progress on a new device, we additionally store your login identifier (your email address, or the identifier provided by Apple/Google).

If we give you Yukigo Pro as a gift (for example because you recommend Yukigo to your followers or help us test the app), we record the gift, its expiry date and the reason on your profile.

This data is hosted on Supabase infrastructure, on servers in the European Union (Sweden), and is used only to provide sync and the features below — never for advertising.

Leaderboards

Taking part in the weekly leagues is your choice. If you take part, your display name, avatar, level, weekly XP and country are visible to the other participants in the leagues, not only to those in your league. You can pick any display name; if you don't pick one, you join with an automatic name ("Student" followed by a number). Only people who earned XP in the last 14 days are placed in the leagues: if you stop, you leave them, and you're back as soon as you study again. You can leave whenever you like with the "Show me on the leaderboard" switch in the app settings: you won't join new leagues, while in the current week's group you stay visible until Monday. Your league history (weekly groups and results) stays linked to your profile until you delete it.

Roles on Discord (optional)

If you tap "Connect Discord" in the app settings, you sign in with your Discord account and allow us to manage Yukigo's linked roles in our Discord server. We keep your Discord ID and username and the access codes Discord gives us, encrypted, linked to your sync profile. We send Discord (Discord Inc., United States) just two numbers: the days you have studied and, if you subscribe to Yukigo Pro, your months of subscription in a row; we update them daily and whenever you open the app settings. They are used only to give you roles in the server. You can disconnect at any time from the app ("Disconnect Discord"): we then delete the data and revoke access. If you remove Yukigo from Discord instead (User Settings → Authorized Apps), we can no longer update your roles; the data stays until you tap "Disconnect Discord" in the app or delete your profile. More details in Discord's privacy policy.

Reminder notifications

Daily reminders (due reviews, streak at risk) are scheduled locally on your device. In addition, if notifications are allowed, the app registers a push notification token on our servers (Supabase) — a technical device identifier issued by the system's notification services — together with the device type (iOS or Android), your app language and timezone. On iPhone, until you choose, the app asks the system for "provisional" permission, with which notifications arrive quietly in Notification Center. Only these are sent from the server: the nudges if you stop (after 8, 14 and 30 days without studying, only between 8 am and 9 pm your time; the 14-day one says how many words you know), the countdown to the exam date you set, and your weekly league result. To decide whether and when to send them, the server also uses your settings (switches, reminder time, exam date and level, holidays), when the app last synced and the history of what was sent. Delivery goes through Expo, Google Firebase Cloud Messaging (Android) and Apple's push notification service (iOS), acting purely as transport channels. You can turn off just the nudges with the "Nudges if you stop" switch, or all reminders with the "Reminder" switch, in the app settings, or by revoking the system notification permission; the token and the history of what was sent are deleted when you delete your account. Never any advertising in notifications.

AI tutor (Yuki)

When you ask Yuki a question, the text of your question, the relevant lesson context (including the answer you chose, if you ask about an exercise), the app language and the latest messages of the conversation (up to 6) are sent to our server and processed by an AI provider (Anthropic, in the United States) to generate the answer; we send Anthropic no identifier of you or of your profile. We keep the text of the questions you type and of the answers, linked to your sync profile, to apply the daily limit and to check and improve the quality of the answers. We do not use your questions for advertising or profiling. Please do not include personal data in your questions.

Pronunciation practice (microphone)

When you use the pronunciation exercises, your voice is recorded only while you hold/tap the record button. The recording is sent to Microsoft Azure AI Speech (servers in the EU, Ireland), which processes it on our behalf solely to produce the pronunciation evaluation. The audio is not stored: we never save it on our servers, the app deletes it from your device when you leave the exercise, and it is not retained by the service after processing. What we do keep: the score, the practiced phrase and the app language, linked to your profile — used only to show your progress and apply daily usage limits. The microphone permission is optional; you can revoke it anytime in your system settings. See Microsoft's privacy statement for details.

Abuse limits

For the AI tutor and the pronunciation exercises we also keep a daily count of requests per IP address, so that no one can overload the service. The IP address is stored only in pseudonymised form (a hash), never in clear, and the counter is not linked to your profile.

Error reporting (crash reports)

If the app runs into an error or closes unexpectedly, we send a technical report to Sentry (Functional Software, Inc.), a crash-reporting service, with data residency in the European Union. The report contains technical data only: the type of error and where in the code it happened, the app's last technical operations before the error (including the addresses of the requests to our servers, which may contain the random identifier of your sync profile), the device model, the operating system version, the app version and a random installation identifier. Your IP address is not stored: on receipt, the service derives only an approximate location (country and city) from it. The report does not contain your identity or your study content, and we do not use it to trace you or your account. We use these reports only to fix defects in the app. See Sentry's privacy policy for details.

Usage statistics (analytics)

To understand which features are useful and where the app needs improving, we collect anonymous usage statistics via PostHog, on servers in the European Union. Events record what gets used (for example: lesson completed, review session finished, exam simulation started), not your study content or your identity: no name, email or account is attached, only a random installation identifier and technical device data (model, operating system, app version). Your IP address is not stored: on receipt, the service derives only an approximate location (country and city) from it. We use this data only to improve the app, never for advertising. You can refuse them at any time with the "Share usage statistics" switch in the app settings: from then on the app stops sending them. See PostHog's privacy policy for details.

Advertising campaign measurement (Apple Ads)

We advertise Yukigo in App Store search results through Apple Ads. To learn which ads work, on iOS devices the app uses AdServices, an Apple service that provides a temporary code revealing only whether the app was downloaded after one of our ads and, if so, the campaign, ad group, search keyword and country. The code does not contain the device's advertising identifier (IDFA) and is not used to follow you across other companies' apps or websites: no tracking, which is why the app does not ask you for tracking permission. The code is sent to RevenueCat (RevenueCat, Inc., United States), which verifies it with Apple on our behalf and links the result to the identifier of your sync profile; to do so it also receives technical data (device model, system and app versions, store country and IP address). We use this information only to understand, by looking at overall numbers, how well our campaigns perform (how many people arrive from each ad, whether they keep studying and, in the future, whether they subscribe) and to decide where to invest: never to show you ads, never sold or shared with others. On Android the app does none of this. When you delete your profile, we also ask RevenueCat to delete the linked data: the request is sent from any device, Android included, and contains only your profile identifier, which we keep until RevenueCat confirms the deletion. More details in RevenueCat's privacy policy.

How you heard about Yukigo (channels and creators)

Some content creators recommend Yukigo and receive a commission on the Yukigo Pro subscriptions of the people they bring to us. To know where people come from, and to work out what each creator is owed, we link the following to your sync profile:

• on Android, the Google Play install referrer: a short label that Google Play passes to the app (the app reads it once, at launch), showing which link brought you to the store (for example a creator's link, yukigo.app/c/…, or one of our posts). It contains neither your name nor any other data about you. On iPhone the App Store gives the app nothing of the kind: Apple only shows us totals;
• your optional answer to "How did you hear about Yukigo?", the question the app asks you once, at the end of a lesson: the channel you pick (for example Instagram or a friend), the creator, if any, and, if you choose "other", the text you write. You can skip the question, with no consequences at all.

We use this data only to understand which channels work and to calculate the creators' commissions: never for advertising. Creators only get overall numbers from us, never who you are. The data is stored on Supabase (EU) and deleted together with your profile. Your answer to the question also reaches the usage statistics (see above), like the other events, without being linked to your profile. If you subscribe to Yukigo Pro, your payments stay on record after the deletion too, so that the creators' accounts add up, but without any data that identifies you.

Contact and feedback

If you write to us — from the "Write to us" button in the app settings, from the invitation to share your opinion, or directly at support@yukigo.app — we receive your email, with your address and whatever you choose to write. The email prepared by the app adds a technical line at the bottom, which you can see and edit before sending: app version, language, level and number of cards studied. We use these messages only to reply to you and to improve the app. Sending them is always your choice.

Newsletter (optional)

If you subscribe to the newsletter, we store your email address and the language of the site you signed up from, and use them only to update you about Yukigo (for example about what's new in the app). Signups are confirmed with double opt-in. Storage and sending are handled by Brevo, a European email service provider that processes the data on our behalf. You can unsubscribe at any time via the link in every email or by writing to support@yukigo.app; on unsubscribing, the address is removed.

Website (analytics)

This website (yukigo.app) uses Vercel Web Analytics: a cookieless, aggregate measurement of traffic (e.g. page views) that collects no personal data and does not track individual visitors. See Vercel's privacy policy. It also uses PostHog (servers in the European Union) to record, again without cookies, page views and a few anonymous events (for example, clicking the buttons to download the app) and, if the link you arrive from carries one, the campaign label (the "utm" parameters, for example that of one of our ads or of a creator's link): no name or email, no profiling of individual visitors; the value of the click identifiers that some platforms add to links (such as Meta's "fbclid") is masked before sending; the IP address is not stored, only an approximate location (country and city) is derived from it. See PostHog's privacy policy. We also advertise Yukigo on Instagram (Meta), with ads that lead to this website: neither the website nor the app uses the Meta pixel or any other Meta tool, so we send Meta no data about you; Meta records clicks on its ads under its own privacy policy and shows us only overall numbers. The site uses no cookies. In your browser it saves only your choice between light and dark theme, if you make one (localStorage), and, for the duration of the visit only (sessionStorage, which the browser clears when you close the tab), the label of the link you arrived from, to pass it on to the store if you tap a button to download the app, and any notice to go back to the app after the link in a confirmation email.

Third-party services

• The app is distributed via Apple's App Store (iOS) and Google Play (Android). As the operators of those stores, Apple and Google may collect technical data relating to the download and use of the app (e.g. crashes and device information) under Apple's privacy policy and Google's.
• Supabase hosts accounts and synced data, on servers in the EU (see above).
• RevenueCat receives, on iOS only, the Apple Ads attribution code and verifies it with Apple to measure our campaigns and, when you delete your profile, from any device, the request to delete the linked data, on servers in the United States (see above).
• Discord receives, if you connect your account, your days of study and months of Pro in a row for the roles in our server, on servers in the United States, and handles them as an independent controller under its own privacy policy (see above).
• Expo, Google Firebase Cloud Messaging and Apple's push notification service deliver push notifications to devices (see above).
• Anthropic processes AI tutor requests (see above).
• Brevo handles newsletter signups and sending (see above).
• PostHog receives anonymous usage statistics, on servers in the EU (see above).
• Sentry receives the app's technical error reports, on servers in the EU (see above).
• Vercel hosts this website and measures its traffic in aggregate form (see above).
• The app's Japanese voice audio files are generated with Microsoft Azure text-to-speech (EU servers) from the app's own teaching content — never from your data — and delivered as audio files; if an audio file isn't available, your device operating system's voice is used instead.
• Microsoft Azure receives the pronunciation-exercise voice recordings (evaluation only, not retained) and generates the app's Japanese voices, on EU servers (see above).

Except where stated otherwise, these providers process data on our behalf, following our instructions and under data processing agreements.

Transfers outside the EU and the UK

The controller is based in the United Kingdom, which the European Union recognises as providing an adequate level of data protection. Some providers (in particular Anthropic for the AI tutor, Expo and Google for push notifications, RevenueCat for campaign measurement on iOS and deletion requests, Discord for server roles, Vercel for the website) may process data in the United States: in those cases transfers take place with the safeguards required by law, such as the standard contractual clauses approved by the European Commission (with the UK addendum) or, for certified providers, the EU-US Data Privacy Framework and its UK extension.

Legal bases

• Performance of the service you ask for: sync, account, leaderboards, AI tutor, pronunciation exercises, delivery of notifications, roles on Discord.
• Consent, which you can withdraw at any time: notification and microphone permissions, newsletter.
• Legitimate interest in keeping the app working, secure and useful: error reports, anonymous usage statistics, abuse limits, measuring our advertising campaigns, measuring the channels people come from and calculating the creators' commissions, replying to the messages you send us.

How long we keep data

• Sync profile, account, tutor questions, pronunciation scores, league history, notification token and history: until you delete them (see "Your rights").
• Abuse counters: 30 days at most.
• Campaign attribution data (RevenueCat): until you delete your profile; after that, we keep the profile identifier only until RevenueCat confirms it has deleted them.
• Discord connection: until you disconnect from the app or delete your profile.
• How you heard about Yukigo (Google Play referrer and your answer): until you delete your profile. Yukigo Pro payments stay after that too, for the creators' accounts, but without any data that identifies you.
• Error reports and usage statistics: for the limited retention period of the respective services, after which they are deleted automatically.
• Newsletter: until you unsubscribe.
• Emails you send us: for as long as needed to reply and to improve the app, or until you ask us to delete them.

No data sale

We do not sell or share your data with third parties for advertising purposes.

Your rights (GDPR and UK GDPR)

You have the right of access, rectification, erasure, restriction of processing, data portability and objection; where processing is based on consent, you can withdraw it at any time, without affecting what happened before. To delete the data stored locally, it is enough to uninstall the app. To delete your sync profile (or account) and all synced data you can use the deletion option in the app's Settings, or write to support@yukigo.app and we will remove it. For any other request, use the same address: we reply within one month.

You also have the right to lodge a complaint with a supervisory authority: in the United Kingdom the Information Commissioner's Office (ico.org.uk), in the European Union the data protection authority of the country where you live. If you can, write to us first: we'll try to sort it out straight away.

Minors

Yukigo is not intended for children under 14. If you are a minor, use the app with the consent of a parent or guardian.

Changes

We will update this policy whenever the way we handle data changes. The date at the top indicates the latest version.