Frequently Asked Questions
Answers to the most common questions about download, reading, AI Key, membership, privacy and sync.
Download & Devices
What versions does Companion Reader offer?
The iOS app is free in supported App Store regions. The web version is not public yet; Android, Windows and macOS remain in testing or planning.
Where are the download links?
Open the "Download" page and follow the App Store link. The current release is free; this site does not offer membership purchases or installers for unreleased platforms.
What if I see a risk warning when installing the APK?
The Android version is still being prepared. Before official release, do not install packages forwarded by others or from unknown sources.
How is the desktop version priced?
The desktop version remains planned and is not for sale. Current work focuses on improving the released iOS reading experience.
Where is the iOS app available?
The iOS app is available in supported App Store regions, but not currently in mainland China. Availability depends on your Apple Account's storefront.
What language does the current iOS app use?
The current overseas iOS release uses an English interface. Future language support will be announced in app updates.
Reading & Library
Can free users read without an API Key?
Yes. Reading, underlining, highlighting, notes and quotes don't need an AI Key. The Key only affects AI chat, summaries, extraction and categorization.
Will my uploaded books be public?
No. Uploaded books are only for your own reading, parsing, sync and AI processing — never public, sold or misused.
What e-book formats are supported?
EPUB is the primary format. More formats will be added based on user demand.
AI & API Key
Whose API does the AI use?
The current app supports user-provided AI API Keys; costs and quotas are determined by the chosen provider. Any future system API will be clearly labeled in the app.
Do I need a membership to use my own API Key?
No membership subscription is available in the current release. Your AI provider generally charges for calls made with your own API Key. Any future membership terms will be announced separately.
Are AI-generated summaries and categories always accurate?
Not always. AI may err — users can refresh, manually edit, or use future correction features. We never claim AI results are always accurate.
Can my API Key be leaked?
We protect Keys via HTTPS, encryption, masking, log sanitization and deletion. You should also set budget limits with your AI provider and reset if suspicious.
Membership & Pricing
What can free users access?
The free version keeps basic reading, bookshelf, underlines, highlights, notes and quotes. Exact limits are shown in the app.
What's the difference between members and free users?
There is no membership subscription in the current release; users can access the available free features. Any future membership benefits, pricing and purchase method will be announced in advance.
Does membership fee include AI provider charges?
There is no membership fee now. When you use your own API Key, your AI provider generally charges you for model calls. Any future system API rules will be explained in the app.
Can I buy iOS membership on the website?
No. The current iOS app has no membership purchase, and this site does not offer external payment. Any future iOS digital membership purchase will be explained in the app.
Data & Privacy
Can I delete my books and notes?
Yes. You can delete books, notes, API Keys and your account. Data is removed or anonymized within a reasonable period, except where law requires otherwise.
Are AI conversations saved?
If the product offers history and sync, AI chats may be saved. Users can view and delete them in-app, per privacy policy and settings.