Shiberu ("we", "us") provides the Shiberu language-learning app and this browser extension. For any privacy question, or to exercise the rights in section 9, contact [email protected]. Shiberu is operated by Stratford Oakham EOOD ("Stratford Oakham" Ltd.), a company registered in Bulgaria (UIC/EIK 207500501, VAT BG207500501), registered office: ul. Racho Dimchev 1, entr. A, fl. 2, apt. 9, Sredets, 1000 Sofia, Bulgaria.

To save cards and sync your progress you sign in with your Shiberu account. The extension keeps your login tokens in its own browser database, which the web pages you visit (and Shiberu's own scripts running inside those pages) cannot read; only its background service worker uses them, to authenticate your requests to Shiberu's own backend. Your profile (such as your email) is kept in that database too. Only your user ID and your language settings (app, native, explanation and target languages) are copied to the browser's local extension storage, where Shiberu's in-page scripts read them to show the extension and its explanations in your languages.

When you study a video with Shiberu, the extension sends the text of its subtitle lines to Shiberu's backend for:

We send the subtitle text itself. We do not send, record, download, or transmit the video or audio stream; the only media that leaves your browser is the screenshot and audio clip of a card you choose to save (section 2.4). On streaming sites we get the caption text from the site's own player: we read the subtitles it loads and, where needed, ask it for them - by turning on a subtitle track, or on Netflix by asking the player to also offer its subtitles as plain text. We never extract anything from the DRM-protected media (see section 6).

Along with the subtitle lines of a supported streaming site (YouTube, Netflix, Crunchyroll, Bilibili, bilibili.tv and Viki), the extension sends that site's ID for the video, its title and, where there is one, the series name. Shiberu uses them only to index the shared cache by episode (section 4); that index holds no account information. For a video on any other website, or a video file on your computer, the extension sends neither the page address nor the page title or any file name - the index files those subtitles under a fingerprint (hash) of their text.

The extension keeps track of which words you know, are learning, or want to ignore, so it can color-code them. These per-word statuses (a word and its status, e.g. "learning") are synced to your account so the same progress shows up across your devices and in the app.

When you choose to save a subtitle line as a flashcard, the extension sends to your account:

You control this - a card is only sent when you save it. Nothing is captured in the background. A card saved while you are offline waits in the extension until it can be sent.

Your settings (display modes, hotkeys, chosen deck) are stored locally and, for some, synced through the browser. The extension can also send anonymous reliability reports about loading subtitles; section 2.7 lists exactly what they contain and how to turn them off.

To keep the extension working as streaming sites change, it may send anonymized diagnostic events about the health of subtitle acquisition. Each event is anonymous, contains no content, and contains no personal information. An event records only:

These events explicitly contain no subtitle text, no page URLs, and no account identifier - they describe the extension's technical behavior, not you or what you were watching. We use them only to detect when a site breaks the extension and to improve reliability. They are optional. On Chrome, turn off "Send anonymous subtitle reliability reports" in the extension's Settings. On Firefox they are sent only if you allow Shiberu Firefox's "technical and interaction data" - when installing, under the add-on's Permissions and data, or with the same switch in Settings.

Everything the extension sends about you or your study goes only to Shiberu's own backend at `https://shiberu.app`, over HTTPS. On the supported video sites the extension also downloads the subtitles of the video you play from that site's own servers (for example YouTube's, Bilibili's or Viki's, and the networks they deliver subtitle files from), the same way the site's own player loads them; it sends those sites nothing of its own. When you play a native speaker recording in the word popup, your browser fetches that audio file from where it is published (the National Institute of Korean Language for Korean, Wikimedia Commons for Japanese and Chinese), like any audio on the web; those servers receive an ordinary request for the file and nothing from your Shiberu account.

AI explanations and text-to-speech run on Shiberu's own self-hosted models, on our own infrastructure. Your subtitle text and words are not sent to OpenAI, Google, Anthropic, or any other third-party AI or translation provider. (Our servers use a standard OpenAI-compatible interface internally to talk to *our own* models - the data does not leave Shiberu's infrastructure.)

We do not use third-party advertising or analytics SDKs in the extension.

To make Shiberu fast and keep AI features free, the results of analyzing a subtitle line and explaining a word are cached and shared across all users. The important part:

These shared caches contain no account data. A cached line-analysis, line translation, AI explanation, or synthesized-audio clip is keyed only by a hash of the text of the line (plus the language). There is no user ID, no account, and no "who watched this" attached to a shared row. If you and a stranger both watch the same episode, you both benefit from the same anonymous cached analysis - but neither of you can be identified from it, and it cannot be traced back to a person.

Your personal data - your word-knowledge statuses and your saved cards - is stored separately, tied to your account, and is never mixed into the shared cache.

Deleting your Shiberu account removes your account-linked data (profile, word statuses, saved cards). Anonymous shared-cache entries, which contain no personal data, are unaffected.

Shiberu is a study tool, not a downloader. On video sites it reads the subtitle/caption text in order to make words clickable and to let you save a line as a flashcard. It does not decrypt, record, download, or redistribute the protected video or audio. The screenshot saved with a card is taken only when you save it, and only where the browser lets a page read the video frame - copy-protected players usually do not, and the card then has none. The optional short audio clip is captured only on sites where the audio is not DRM-protected; on protected services (e.g. Netflix) no audio is captured and synthesized speech is used instead. Your use of each streaming service remains subject to that service's own terms.

Shiberu is not directed at children under 13 (or the minimum age in your country). We do not knowingly collect data from children.

Depending on where you live (including under the GDPR in the EU/EEA and the UK), you have the right to access, correct, export, or delete your personal data, and to withdraw consent. You can:

Our legal basis for processing is the performance of the service you asked for (making subtitles interactive and saving your cards) and your consent, which you can withdraw at any time by logging out or uninstalling.

We do not sell your personal data, and we do not share it with third parties for their own purposes. We do not send your study text to any third-party AI provider. Data is processed only to provide the Shiberu service.

If we materially change what the extension collects or how it's used, we'll update this page and its "Last updated" date, and where appropriate notify you in the app or extension.