Privacy Policy

JStacked ("we", "us", "our") is a Japanese language learning tracker operated by an individual based in Florida, United States. You can reach us at hello@j-stacked.com.

We collect only what is necessary to provide the service:

• Email address — used to send you a magic link to sign in. We do not store your password.
• Study activity data — lesson counts, review counts, streaks, and JLPT progress synced from connected apps (WaniKani, BunPro, Renshuu). This data is fetched using API keys you provide and stored to power your dashboard.
• Target JLPT level — set during onboarding, used to personalise your readiness metrics.
• Payment information — if you subscribe to JStacked Premium, payments are processed by Stripe. We never see or store your card details.

We do not collect your name, phone number, address, or any social media profile information.

• To operate and personalise your JStacked dashboard
• To authenticate you via magic link (email)
• To sync study data from your connected apps on your behalf
• To process subscription payments via Stripe
• To improve the service based on aggregate, anonymised usage patterns

We do not sell, rent, or share your personal data with third parties for marketing purposes.

JStacked uses the following third-party services, each with their own privacy policies:

• Supabase — database and authentication hosting (supabase.com/privacy)
• Vercel — web hosting and deployment (vercel.com/legal/privacy-policy)
• Stripe — payment processing (stripe.com/privacy)

We use a single session cookie to keep you signed in. This cookie is strictly necessary for the service to function and does not track you across other websites. We do not use advertising or analytics cookies.

Your data is retained for as long as your account is active. You can request deletion of your account and all associated data at any time by emailing hello@j-stacked.com. We will process deletion requests within 30 days.

All data is transmitted over HTTPS. Your study app API keys are stored encrypted in our database. Access to your data is restricted by row-level security — no other user can access your information.

JStacked is not directed at children under the age of 13. We do not knowingly collect personal information from children. If you believe a child has provided us with personal data, please contact us and we will delete it promptly.

You have the right to access, correct, or delete the personal data we hold about you. To exercise any of these rights, email us at hello@j-stacked.com.

We may update this policy from time to time. When we do, we will update the date at the top of this page. Continued use of JStacked after changes constitutes acceptance of the updated policy.