Legal.

Privacy policy

Kios is built to keep your reading to yourself. Your library, your highlights and your statistics live on your device — not on our servers.

Last updated · 2 June 2026

The short version

Kios is a reader for books you already own. We don't run ad networks, we don't sell data, and we don't build a profile of you. Your reading content stays on your device. The only things that leave it are the sync traffic you opt into by connecting a sync service, and anonymous crash & performance diagnostics (detailed below).

What stays on your device

The following is stored locally on your iPhone and is never sent to us:

  • Your imported EPUB books and their covers
  • Reading progress, bookmarks, highlights and notes
  • Reading statistics — read-time, pages, streaks and history
  • Your app preferences, such as themes and typeface

Optional sync

If you choose to enable a sync service, Kios sends only what that service needs to keep your reading position in step:

  • KOReader Sync — the server address, your username, and reading-position data, sent directly to the sync server you configure.
  • Kobo Sync — the credentials and progress data required by the Kobo sync endpoint you configure.

These connections are made to the servers you enter. Kios does not operate these servers and does not receive a copy of that data. Sync is off until you turn it on, and can be removed at any time.

Crash & performance diagnostics

Kios includes no advertising SDKs, no usage-analytics services, and no tracking identifiers. The released app (TestFlight and the App Store) does collect crash and performance diagnostics so we can find and fix crashes and stability problems:

  • What — crash reports, app-hang and watchdog reports, a sampled set of performance traces, and the technical context at the moment of an error: call stacks, the on-screen view layout, and device/OS details. Never the contents of your books, highlights or notes.
  • Where — these reports are sent to Sentry (operated by Functional Software, Inc.), hosted in the United States.
  • Who — each report carries only an anonymous, random per-install identifier (it resets if you reinstall), used to count how many installs a crash affects. No name, email, account, or IP address is attached.

Development builds send nothing. Apple may also report aggregated crash and usage data through App Store Connect if you have opted in under Settings → Privacy & Security → Analytics & Improvements; that is governed by Apple, not Kios.

Data we never collect

We do not collect your name, contacts, location, advertising identifier, or the contents of your books and notes.

Children

Kios is not directed at children under 13 and does not knowingly collect personal information from them.

Changes to this policy

If this policy changes, the "last updated" date above will change with it. Material changes will be noted in the app or on this page.

Contact

Questions about privacy in Kios? Reach us on Discord or at [email protected].