DuoSub — Privacy Policy

Last updated: 21 August 2026

DuoSub lets you watch online videos with dual subtitles and AI translation. This page explains what the app collects, why, and how to delete it.

What we collect

• Account — when you sign in with Google or Apple we receive your email address and, if you allow it, your name. Apple's Hide My Email is fully supported; we never need your real address. Sign-in is required because the free translation allowance is counted per account.
• Usage of the translation service — how many translations you have used today, and the identifier of the video being translated. We do not store what you watch as a viewing history.
• Subscription status — if you subscribe to DuoSub Pro, we store the Apple transaction identifier and the expiry date so the app knows your subscription is active. Apple never shares your payment details with us.

What we do not collect

DuoSub contains no advertising and no analytics SDK of its own. We do not use your device's advertising identifier (IDFA), we do not track you across other apps or websites, and we never sell or share your data with data brokers.

Videos play through YouTube's official embedded player, and YouTube may show its own ads before or during a video, exactly as it does on youtube.com. Those ads are served and measured by Google under Google's own privacy policy — we do not select them, we receive no data about them, and we earn nothing from them.

The in-app browser

The Browse tab is a plain web browser. Whatever page you open there is loaded directly from that website, exactly as your normal browser would load it — we do not proxy it, we do not modify it, and we do not log which pages you visit.

Because it is a real browser, the sites you visit can set cookies and local storage, and those are kept on your device so you are not asked the same cookie question every time you open the tab. That storage is separate from the rest of the app: it is never read by DuoSub, it is not sent to us, and signing in to a website there does not sign you in to DuoSub. Deleting the app deletes it.

When you tap a YouTube video in that tab, the only thing DuoSub takes from the page is the video ID, so it can fetch that video's subtitles. Nothing else is read.

What stays only on your device

Your saved videos, playback positions, downloaded subtitles, app settings and everything the in-app browser stores are kept on your device and are not uploaded to us.

Who we share it with

We do not sell your data. We use these processors, and only for the purposes listed:

• Google Firebase — sign-in, database, and abuse prevention (App Check).
• Google Gemini — subtitle translation. Only the subtitle text is sent; it is never linked to your account or identity.
• Apple — payments and subscription management.

Deleting your data

Open Settings → Delete account inside the app. This permanently deletes your account, your translation allowance and your subscription record. It cannot be undone. You can also email us and we will do it for you.

Children

DuoSub is not directed at children under 13, and we do not knowingly collect their data.

Contact

Questions or requests: huyloind03w@gmail.com

Support · About DuoSub