Sayover Privacy Policy
Effective date: October 1, 2026
unstackd ("we") operates Sayover, a Chrome extension ("Sayover"). This policy explains what information Sayover handles, where it is kept and how you can delete it. The Korean version is the governing text; if the versions differ, the Korean version prevails.
1. Summary
- Sayover has no accounts and no servers, and sends nothing to us.
- Your learning data is stored only inside your browser. We cannot see it.
- No ads, no analytics, no tracking cookies. We never sell or share your information.
2. What Sayover stores in your browser
To make its learning features work, Sayover stores the following in your browser's local storage (the extension's own IndexedDB and chrome.storage). None of it leaves your device.
| Data | What it is | Used for |
|---|---|---|
| Saved sentences | English caption lines you save with S, the lines before and after, the matching translated caption, and the time in the video |
Saved list, review |
| Video info | ID, title and channel name of YouTube videos you saved sentences from | Opening the video from your saved list |
| Review history | Review dates, ratings (Again/Hard/Good/Easy), next review date | Spaced-repetition (FSRS) scheduling |
| Watch history | IDs of YouTube videos watched with Sayover on, time watched, number of translation reveals (T), number of saves |
Your own learning stats |
| Settings | Native language (Korean/Japanese), which tips you've seen, the review in progress | Display |
3. Permissions and why
- storage — to keep the data and settings above in your browser.
- Access to youtube.com — to show the caption overlay on YouTube videos and read the English and translated captions of the video you are watching. Sayover does not run on any other site.
Captions are requested by your browser directly from YouTube, the same way the YouTube player requests them. We are not involved in these requests; Google's Privacy Policy applies to your use of YouTube.
4. Retention and deletion
- Your data stays in your browser until you delete it or remove Sayover.
- Delete saved sentences one by one from the saved list.
- Delete everything with [Delete all data] in the saved list or the popup: saved sentences, review history, watch history and settings are removed at once. Removing Sayover at
chrome://extensionsalso deletes all Sayover data in your browser. Deleted data cannot be recovered, including by us. - Backups you create with [Export] are saved on your device only and are never sent to us. Please export a backup before removing Sayover.
5. Emails to us
If you email hello@sayover.app, we process your email address and message to reply.
- Purpose: answering your inquiry only (never marketing).
- Retention: deleted within one year after the inquiry is resolved, unless the law requires longer.
- Processors and international transfer: emails pass through Cloudflare, Inc.'s email forwarding (USA) and are delivered to and stored in Gmail by Google LLC (USA). If you do not want this transfer, please do not email us (we then cannot reply).
6. Your rights
You can access, correct, delete or restrict the processing of your information at any time. Sayover's learning data is only in your browser, so you can view it (saved list) and delete it yourself. For requests about emails you sent us, contact hello@sayover.app and we will respond without delay. Depending on where you live (for example the EU/UK under the GDPR, or California under the CCPA), you may also lodge a complaint with your local data protection authority.
7. Children
Sayover is not directed at children under 13 (under 14 in Korea).
8. Contact
- Operator: unstackd (Bumjin Cho, Representative and Privacy Officer)
- Email: hello@sayover.app
9. Changes
If we add features that send information off your device — such as accounts, sync, payments or AI explanations — we will update this policy before those features ship and announce it on this page and in the extension. Past versions are listed at the bottom of this page.
10. Other
Sayover is not affiliated with or endorsed by YouTube or Google. YouTube is a trademark of Google LLC.
History: October 1, 2026 — first version