Hey LinPrivacy Policy
Hey Lin is an iPhone app where you talk with Lin, an AI character. This policy explains what data the app and this website handle, where it goes and how long it's kept. “Hey Lin”, “we” and “us” mean the operator of the app.
The short version
- Your voice never leaves your phone. Speech is turned into text on your iPhone, and Lin's voice is generated on your iPhone.
- Only text goes to the cloud, to write her replies: through our server to an AI model provider (DeepSeek, with Google's Gemma 4 on Cloudflare Workers AI as a backup).
- Our server doesn't store your conversations and keeps no IP address or request logs.
- Your chats, her memories and her diary stay on your iPhone. You can delete them anytime.
- No account, no ads, no tracking, no analytics. We don't sell data.
What stays on your iPhone
- Your voice. During a call, the sound from the microphone is turned into text on your iPhone by Apple's on-device speech recognition. The audio is not sent to us or to anyone else.
- Her voice. Lin's voice is generated on your iPhone by a voice model (about 1 GB) that ships inside the app.
- Your conversation history, what she remembers, her diary and your profile (the name, gender and age range you gave her) are stored in the app's private storage on your iPhone. We don't have a copy.
- How much of the free trial you've used is kept in your iPhone's keychain, so the trial isn't restarted when the app is reinstalled. iOS may keep this small record after the app is deleted.
If you back up your iPhone to iCloud or a computer, iOS may include the app's data in that backup, as it does for other apps. Those backups are handled by Apple and your own settings, not by us.
What is sent to the cloud, and why
Lin's replies are written by an AI model in the cloud. Each time she replies, the app sends the following text over an encrypted connection to our server, api.heylin.app, which runs on Cloudflare:
- what you just said or typed, as text;
- the recent conversation;
- the things she remembers about you;
- the name, gender and age range you gave her;
- the language she speaks, the current date and time on your iPhone, and the crisis helpline for your region (so she can point you to it if you need it).
Similar text is sent when she tidies up her memory (the list of things she remembers) and when she writes a diary entry (that day's conversation and your profile).
Our server passes the text to an AI model provider, which writes the reply, and sends the reply back to your iPhone. The main provider is DeepSeek. If it fails, Gemma 4, Google's open model, running on Cloudflare Workers AI is used as a backup. Our server doesn't store the text or the reply.
To protect the service from abuse, requests also carry a proof from Apple's App Attest that they come from the genuine app on a real iPhone and, if you subscribe, your subscription receipt so the server can check it.
What our server stores
Our server doesn't store conversations and keeps no request logs or IP address logs. For each installation of the app, it stores only:
- the App Attest key ID and public key that your iPhone created for the app, and a counter used to reject repeated requests;
- how many requests were made during the free trial and on each day (to enforce the free trial and the daily fair-use limit), when the installation was first and last seen, the app version, and whether it has been blocked for abuse;
- reports you send us (see “Reports” below).
This data is tied to an anonymous key generated on your iPhone. It contains no name, email address, Apple Account, phone number or location. Subscription receipts are checked but not stored. Like any internet service, Cloudflare, which runs our server, handles your IP address to deliver requests; we don't log or keep it.
AI model providers
DeepSeek and Cloudflare process the text they receive under their own terms and privacy policies. DeepSeek is a company based in China and processes the text on its servers. We don't sell your data, don't use it for advertising and don't use it to train AI models ourselves.
Subscriptions and payments
Purchases are handled entirely by Apple. We never see your payment details, your name or your Apple Account. To check whether you've subscribed, our server verifies the receipt Apple provides and doesn't store it.
Reports
If you report something Lin said, that line and the reason you chose, along with the language and the app version, are sent to our server and stored with your installation's anonymous key so we can review it (within 24 hours) and improve her. The rest of your conversation is not sent.
Permissions
| Microphone | Used only during calls, to hear what you say. The sound is processed on your iPhone and never uploaded. |
|---|---|
| Speech Recognition | Used only during calls, to turn what you say into text on your iPhone. |
The app doesn't ask for your location, contacts, photos or camera, and doesn't ask to track you. You can change permissions anytime in your iPhone's Settings.
What we don't do
There's no account or login. There are no ads, no tracking across apps or websites and no analytics SDK in the app. We don't sell your data or share it for advertising.
This website
This website has no cookies, ads, analytics or trackers. If you pick a language, the choice is saved in your own browser (localStorage) and never sent to us. The site is served by Cloudflare with request logging turned off; Cloudflare handles connection data such as IP addresses to deliver the pages and protect them from attacks.
Adults only
Hey Lin is only for people 18 and older. The first time you open the app, it asks your age range and doesn't let under-18s continue. We don't knowingly collect data from children. If you believe a child is using the app, please contact us.
How long data is kept
Data on your iPhone stays until you delete it or delete the app. On our server, the text sent to write a reply is not stored; the AI providers may keep it as their own terms allow. Per-installation data (the App Attest key, the counter and usage counts) is kept as long as it's needed to run the service and prevent abuse. Reports are kept as long as needed to review them and improve Lin.
Your choices and rights
You can see and delete what Lin remembers in Settings → What Lin remembers, one item at a time or all at once. Deleting the app removes everything stored on your iPhone. The data on our server is tied only to an anonymous key, not to you, so we usually can't tell which records are yours; if you'd like to access or delete anything server-side, or have a question about it, write to support@heylin.app and we'll help as far as we can. Depending on where you live, you may also have the right to complain to a data protection authority.
International transfers
Our server runs on Cloudflare's global network, and the AI providers may process text outside your country, including in China (DeepSeek). Data protection laws there may differ from those where you live. We send only what's needed to write Lin's replies.
Security
Connections between the app, our server and the AI providers are encrypted (HTTPS). App Attest lets our server accept requests only from the genuine app. No system is perfectly secure, so we keep what we store to a minimum.
Changes to this policy
If we change how data is handled, we'll update this page and the date at the top before the change takes effect.
Contact
Questions about privacy: support@heylin.app