Privacy Policy — Dual Subs
Last updated: June 13, 2026 Extension: Dual Subs (Chrome Extension) Contact: infodualsubtitle@gmail.com
Dual Subs is a browser extension that displays dual subtitles and an inline dictionary on Netflix, YouTube, Amazon Prime Video, and Disney+. This policy explains what data the extension handles, where it is sent, and your choices. We have tried to keep it plain and accurate to what the code actually does.
1. Summary
- You can use almost all features without an account. Sign-in is optional and only enables cloud sync.
- We do not sell your data, show ads, or use third-party trackers/analytics.
- The extension reads subtitle data from the page only to display dual subtitles and to look up words you click.
- When you click a word, that word (and, for Spanish, the surrounding subtitle sentence) is sent to a dictionary/translation service to fetch its definition.
- If you sign in, your saved vocabulary and settings are stored in our cloud database (Supabase) so they sync across devices.
2. Data We Handle
2.1 Stored locally on your device (chrome.storage.local)
Used to make the extension work. Stays on your machine unless you sign in and sync.
- Preferences: primary/secondary language, subtitle size, color, font, overlay position, interface language (ES/EN), enable/disable state.
- Saved vocabulary: words you choose to save, with their reading, meaning, language, the subtitle sentence they appeared in (context), status (known/learning/unknown), and the date saved.
- Optional API key: a personal KRDICT (Korean dictionary) key, only if you enter one.
- Session tokens: if you sign in, your authentication tokens are stored locally so you stay logged in.
2.2 Account data (only if you sign in)
- Email address and account identifier, used to authenticate you and associate your synced data with your account.
- Sign-in is handled on our website (
dual-sub-insight.lovable.app) via email/password or Google. The website returns a session token to the extension. We never see or store your password inside the extension.
2.3 Data sent to our cloud (only if you sign in and sync)
When signed in, the following is stored in our database (Supabase) under your account:
- Your saved vocabulary words (word, meaning, language, context sentence, status, date).
- Your settings/preferences.
Each user can only access their own data (enforced by row-level security).
3. Subtitle Content
To show dual subtitles, the extension reads the subtitle/caption data already delivered to your browser by the streaming platform. This processing happens locally in your browser. Full subtitle text is not sent to us or to any third party — with two exceptions you trigger yourself:
- Word lookups: when you click a word, that single word is sent to the relevant dictionary service to fetch a definition.
- Spanish word analysis: when you click a word and your interface is set to Spanish, the surrounding subtitle sentence may be sent to a grammatical-analysis service (Apertium) to identify the word's base form. This sentence is used only for that lookup and is not stored by us.
4. Third-Party Services
The extension contacts the following services. Most receive only the word (or short text) you are looking up. We do not control their data practices; please review their own policies.
| Service | What is sent | Purpose |
|---|---|---|
| Supabase (our database/auth) | Account email, session tokens, your saved vocabulary & settings | Login and cloud sync |
| Our website (dual-sub-insight.lovable.app) | Login credentials you enter there | Authentication (incl. Google sign-in) |
| Jisho.org | The Japanese word clicked | Japanese definitions |
| Wiktionary (en/es and others) | The word clicked | Definitions |
| dictionaryapi.dev | The English word clicked | English definitions |
| KRDICT (krdict.korean.go.kr) | The Korean word clicked | Korean definitions |
| jsDelivr CDN (CC-CEDICT data) | The Chinese characters clicked | Chinese definitions |
| MyMemory (api.mymemory.translated.net) | The short text being translated | Translating definitions to Spanish |
| Apertium (apertium.org) | The word and its subtitle sentence (context) | Spanish base-form analysis |
| YouTube (timedtext) | Subtitle track request for the current video | Fetching YouTube subtitles |
We do not send your account information to any of the dictionary/translation services above — only the text being looked up.
5. How We Use Data
We use the data only to:
- Provide the dual-subtitle and dictionary features.
- Save and sync your vocabulary and preferences (when signed in).
- Authenticate you and keep you signed in.
We do not use your data for advertising, profiling, or sale, and we do not share it with third parties except the service providers listed above that are necessary to deliver the features.
6. Data Retention and Deletion
- Local data stays until you clear it (remove saved words in the popup, or uninstall the extension, which clears local storage).
- Cloud data is kept while your account exists. You can delete your saved words from within the extension. To delete your account and all associated cloud data, contact us at the email above.
7. Security
- Communication with our servers and dictionary services uses HTTPS.
- Cloud data is protected by per-user access controls (row-level security) so users can only access their own records.
- Session tokens are stored in the browser's extension storage and are not exposed to web pages.
No method of transmission or storage is 100% secure, but we take reasonable measures to protect your data.
9. Website (dual-sub-insight.lovable.app)
This section covers what happens on our website specifically (separate from the extension itself).
9.1 What the website is for
The website is a companion to the extension. It lets you create an account, sign in, manage your saved vocabulary in a dashboard, take quizzes, change settings, and send feedback. It also acts as the auth bridge that signs you into the Chrome extension.
9.2 Account & sign-in
You can sign in with:
- Email and password — your password is handled by our authentication provider (Supabase) and is never seen or stored by us.
- Google sign-in (OAuth) — when you choose Google, Google shares with us your name, email address, profile picture, and Google account ID so we can create your account. We do not receive your Google password and do not access any other Google data (no contacts, no Drive, no calendar, etc.).
9.3 Auth bridge for the Chrome extension
When you open the website with a special link from the extension (/auth?ext=<extensionId>), after you sign in your session token is sent to the extension via Chrome's secure messaging API and the tab closes automatically. No additional data is collected during this step.
9.4 Dashboard data
While signed in, the dashboard reads and writes the following under your account in our database:
- Vocabulary — words you saved, with meaning, language, the subtitle sentence (context), status, and date.
- Quiz progress — which words you've practiced and your results.
- Settings & profile — your preferences and display name.
- Feedback — any message you submit through the feedback form is stored so we can read and respond.
Per-user row-level security means each account can only read or modify its own data.
9.5 Cookies & local storage on the site
The website only uses storage that is necessary to make it work:
- An authentication session so you stay signed in.
- Your interface language (English/Spanish) preference.
We do not use analytics cookies, advertising cookies, or third-party trackers on the website.
9.6 Payments
The website does not currently process any payments. The subscription page is informational only. If we add real billing in the future, this policy will be updated before any charge is made and the payment processor will be disclosed here.
10. Children's Privacy
Dual Subs is a general-audience language-learning tool and is not directed to children under 13. We do not knowingly collect personal information from children.
11. Changes to This Policy
We may update this policy. Material changes will be reflected by updating the "Last updated" date above and, where appropriate, noted in the extension or on our website.
12. Contact
Questions or requests (including data deletion): infodualsubtitle@gmail.com