Privacy Policy
Last updated August 10, 2026
OneLine ("we," "us") builds a daily writing habit app. This policy covers what we collect through the app and this site, and how we use it.
What we collect
- An anonymous device-based account — no email or name required to start. You can optionally link an email later to keep your streak across devices.
- The sentences you submit, your CEFR level, chosen language, feedback strictness, and streak history.
- Basic usage data (app opens, notification taps) so we can tell if the product is working.
- Push notification tokens, to deliver your daily prompt.
How we use it
Your sentences are sent to our AI provider to generate a grammar correction and, for the corrected version, a spoken-audio file. Your data isn't used to train third-party models beyond what your provider's standard API terms disclose, and we don't sell it.
Who we share it with
- Supabase — hosts our database, authentication, and backend functions.
- Our AI correction provider — processes the sentence you submit to produce a correction.
- Our text-to-speech provider — generates the native-audio playback of corrected sentences.
- Expo (Expo Application Services) — delivers push notifications.
- PostHog — product analytics (app opens, feature usage; never the text of your sentences).
- RevenueCat and your app store — handle Pro subscription billing; we don't see or store your card details.
Your choices
You can delete your account and all associated data from Settings at any time. If you linked an email, you can also request a copy of your data by contacting us below.
Children
OneLine isn't directed at children under 13, and we don't knowingly collect data from them.
Changes
If this policy changes materially, we'll update the date above and notify you in the app.
Contact
Questions about this policy: support@one-line.app