Privacy Policy
LangTube — Last updated: April 13, 2026
Overview
LangTube is a YouTube English learning assistant that provides bilingual subtitles, click-to-lookup dictionary, and vocabulary management. It is designed with privacy as a core principle: all subtitle processing, dictionary lookups, and vocabulary data are stored locally in your browser.
Data We Collect
We collect the absolute minimum data required to operate the extension:
- License Key: When you activate a paid license, your license key is sent to our verification server to validate your subscription status.
- Email Address: The email address associated with your license purchase, used solely for license management and support communication.
Data We Do NOT Collect
- We do not collect, store, or transmit your YouTube viewing history or video content.
- We do not collect your vocabulary data, saved words, or dictionary lookups.
- We do not collect your browsing history or browsing activity.
- We do not use any analytics or tracking services.
- We do not collect any personally identifiable information beyond what is listed above.
- We do not sell, rent, or share any user data with third parties.
Data Storage
All data generated by the extension is stored locally on your device using browser-native storage technologies:
- IndexedDB for vocabulary entries, translation cache, and dictionary cache.
- chrome.storage.local for extension settings, license status, and UI state.
Your vocabulary book, saved words, and study progress never leave your browser unless you explicitly export them (CSV or Anki .apkg files saved to your device).
YouTube Subtitle Access
LangTube accesses YouTube's subtitle/caption data through YouTube's public timedtext API. This is the same data that powers YouTube's built-in subtitle feature. LangTube does not modify, record, or redistribute video content.
The extension only activates on YouTube pages (www.youtube.com). It does not run on or access any other websites.
Translation Service
Subtitle translation uses Google Translate's public API endpoint. The subtitle text is sent to Google's servers for translation. No user identification data is included in these requests. Translation results are cached locally to minimize repeated requests.
Dictionary Lookups
Word definitions are fetched from the Free Dictionary API (api.dictionaryapi.dev) and Wiktionary as a fallback. Only the looked-up word is sent; no user or context data is included. Results are cached locally in IndexedDB.
License Verification
When you enter a license key, the extension sends a request to our verification server containing:
- Your license key
- The product identifier (
langtube)
No vocabulary data, subtitle content, browsing data, or other personal information is included in this request.
Third-Party Services
- Stripe is used to process payments for Pro plans. Payment information is handled entirely by Stripe and is never stored on our servers. See Stripe's Privacy Policy.
- Google Translate API is used for subtitle translation. See Google's Privacy Policy.
- Free Dictionary API is used for word definitions. This is a free, open-source service.
Permissions
The extension requests only the permissions necessary for its core functionality:
- storage: To save your vocabulary, settings, and license status locally.
- identity: For future Notion OAuth integration (Pro feature, coming soon).
- Host permission (youtube.com): To detect YouTube video pages and inject bilingual subtitles.
- Host permissions (translate, dictionary APIs): To fetch translations and word definitions.
Changes to This Policy
We may update this privacy policy from time to time. Any changes will be posted on this page with an updated revision date. Continued use of the extension after changes constitutes acceptance of the updated policy.
Contact Us
If you have questions or concerns about this privacy policy, please contact us:
- Email: support@extpilot.com
- Website: extpilot.com