Privacy
Updated 16 September 2026
Bunbuku is an independently developed Japanese learning app. This page covers the Bunbuku website, web app, and mobile apps. For privacy questions or requests, contact support@bunbuku.com.
Information we use
- Account information: your email address, sign-in identifiers and display name, where provided. Our authentication provider manages passwords and sign-in sessions.
- Guest identity and preferences: a device identifier, reading and audio settings, and other information needed to continue your learning. Signing in can connect your guest progress to your account.
- Learning information: lessons and activities, practised vocabulary, review schedules, conversation history, corrections, scores, practice days and progress.
- Information you choose to share: messages, feedback, and details such as your name, country, occupation or interests when you use personal lesson activities. Avoid sharing sensitive information you do not need for learning.
- Audio: microphone recordings are sent for speech transcription. Bunbuku uses temporary recordings during processing and does not keep them as conversation history. Conversation text is stored. Generated speech may be cached for playback.
- Subscription information: on the web, Stripe processes checkout and card details. Bunbuku stores customer/subscription references and access status, not full card numbers. In the iOS and Android apps, Apple or Google processes subscriptions. We exchange an opaque account reference and purchase records with the store to verify access and handle renewals.
- Technical information: servers and service providers process network and device information to deliver the service, diagnose failures, secure accounts and enforce usage limits.
Speech and AI processing
Google Cloud Speech-to-Text processes recordings to produce text. Google Gemini processes relevant conversation text and lesson inputs to generate responses, examples and feedback. Google speech services generate audio for playback. Your messages may contain personal information you choose to include. AI responses can be incorrect.
We use these inputs to provide the learning features you request. We do not use your conversations to train our own AI models. Provider processing is governed by the applicable service terms and our provider configuration.
Service providers
| Provider | Purpose |
|---|---|
| Supabase | Authentication and storage of account, conversation and learning data |
| Google Cloud and Gemini | Backend hosting, speech transcription, AI responses and feedback, generated audio and audio-cache storage |
| Vercel | Website and web-app hosting |
| PostHog EU | Usage analytics, such as pages visited, activity completion, timing and acquisition source, linked to a device or account identifier when enabled |
| Sentry | Error and performance diagnostics |
| Apple App Store and Google Play | Native subscription purchases, payment processing, verification and subscription management |
| Stripe | Optional web subscriptions, payment processing and billing management |
| Google Fonts | Serving website fonts; font requests include ordinary network information |
Bunbuku does not sell your personal information or use advertising identifiers. We keep learner transcripts, names and email addresses out of authored analytics events. Providers may process information in countries outside your own. You can contact us for information about the processing arrangements and applicable safeguards.
Cookies and browser storage
We use cookies and similar storage, including local storage and IndexedDB. Necessary storage keeps you signed in, recognises guest progress and remembers your choices. Usage analytics helps us understand how people discover and use Bunbuku. Website browsing is available without analytics. Free learning in the web app requires the usage-data agreement shown before entry; existing active Pro, founding and partner access is preserved without that agreement.
| Storage | Purpose and duration |
|---|---|
| Guest device identifier | Necessary to connect your activity to your browser. The guest cookie has a configured lifetime of up to 400 days; browser restrictions may shorten it. Other local copies remain until cleared. |
| Sign-in and learning preferences | Necessary authentication/session and local preference storage. Retained until expiry, sign-out where applicable, or clearing the relevant storage. |
| fluent_analytics_consent | Remembers your analytics choice for up to 180 days across the Bunbuku website and web app. An app-access agreement also records its notice version and decision time in this cookie. It is specific to this browser, not a permanent account record. |
| PostHog analytics storage | Cookies and local storage for usage measurement and acquisition attribution. Configured cookie lifetime: 90 days. Disabled until you allow analytics on the website or agree in the web app. |
You can decline analytics and continue browsing this website. In the free web app, Agree and continue enables learning; Leave Bunbuku returns to the website. You can withdraw through Analytics choices in app Settings or here. Withdrawal stops further web analytics and clears its browser storage. Free learning then requires a new agreement. Account settings, sign-in, billing, support and deletion remain available, and existing active Pro, founding and partner access is not removed. Withdrawal does not delete your learning history or automatically erase earlier analytics records. Contact us if you want those records removed.
Native apps use app storage rather than browser cookies. You can turn off usage analytics in Settings. Diagnostic processing needed to investigate errors is separate from optional usage analytics.
Why we use information
We process information to provide the learning features and account services you request, handle subscriptions, protect the service and respond to support requests. Where applicable, these purposes rely on providing our service, legitimate interests in security and reliability, or legal obligations. Web usage analytics starts after your explicit choice. The app-access notice explains the consequence for free web learning before you agree.
Retention and deletion
Account-linked learning history stays available while your account exists unless you delete it. Guest history remains linked to its device identifier until removed; clearing browser storage alone does not delete server-side history. Temporary microphone files are cleaned up after processing. Provider logs, caches, backups and billing records have separate retention arrangements, including records that must be kept for legal or accounting reasons.
In Settings, Delete account removes your application data and authentication account and cancels a linked Stripe subscription. Apple and Google subscriptions must be cancelled separately through the store. Provider records, including earlier analytics, may require a separate erasure request. We can help you identify and request removal of those records. See account deletion and data requests.
Your choices and rights
You can edit available preferences in Settings, change your web analytics choice as described above, and request access, correction, a copy or deletion of your personal information. Depending on the law that applies, you may also have rights to object to or restrict processing and complain to a data protection authority. Contact us from your account email when possible; we may need to verify a request to protect your information.
For privacy requests, email support@bunbuku.com. We will explain any information we need to retain and why. Material changes to this policy will be reflected here with an updated date.