How the OK-Mine website and browser extension handle data.
OK-Mine is a free tool for building Japanese study decks from YouTube channels. All of it works without an account — nothing below changes unless you choose to sign in (see “If you sign in”).
When you start mining a channel on okmine.app, the OK-Mine browser extension fetches the caption/transcript text of the videos you choose, using your own internet connection, and returns that text to okmine.app. The extension does not read your YouTube account or your YouTube watch history, and it observes no browsing activity — with one exception you control: the optional immersion tracking described below, which is off by default.
If you switch on “Track immersion on YouTube” in the extension's popup, the extension measures how many minutes of video you watch — but only on YouTube watch pages and in okmine.app's own embedded players, and only for creators that are in the OK-Mine catalog. Videos by other creators, YouTube search, comments, recommendations, and all other browsing are never recorded.
This data stays on your device unless you sign in — signed out it is stored inside the extension (your browser's local extension storage) and is never transmitted to the OK-Mine server or anyone else; the immersion stats on okmine.app/me.html read it directly from the extension in your browser. If you sign in, it is additionally backed up to your account so your other devices can show it (see “If you sign in”). You can export it as a file, delete it at any time from the extension popup (“Clear immersion data”), or remove it entirely by uninstalling the extension.
Fetched transcripts (public YouTube captions) are cached on the OK-Mine server so other users mining the same channel get them instantly. We do not collect names, emails, IP-based profiles, or any personally identifiable information.
You can optionally sign in with Google to back up your OK-Mine data and sync it across devices. Signing in is never required — every feature works without it, and signed-out users send us nothing personal at all.
If you do sign in, we store exactly this, on our own server in the EU (Hetzner, Germany): your email address from Google (used only to identify your account, contact you about it if ever needed, and delete it on request — we receive no other Google data, no watch history, no YouTube account access), and the study data you sync — your known words, level, interests, saved channels, comprehension progress, streak, and (if you use the extension's tracking) your immersion watch history.
These payloads exist only to give them back to you on your devices. We never analyze them, build profiles from them, share them, or use them for anything else. Deleting your account (the button on your page, or an email to us) permanently removes the account and every synced copy from our server; the data on your devices is yours and stays untouched.
To see whether OK-Mine is useful, we keep anonymous, aggregate counts of actions — e.g. “a deck was built” or “a transcript was fetched.” These are simple daily tallies with no names, IP addresses, cookies, or any identifier; they can't be traced back to you or a specific device.
We do not sell or share your data, show ads, or track you across sites. There are no third-party processors beyond Google's sign-in itself.
Last updated: 2026-07-16