Watch YouTube. Learn the language.
Doublet puts two subtitle lines on any YouTube video: the language you're learning and your own. Click a word or drag across a phrase to see what it means, save it, and review it later with flashcards.
| Time | Lang | Original line | Your language | New words |
|---|
Click any word on the video
Words you haven't seen are underlined. Words you're learning glow amber. Known words fade into the line. Try it: click a word below.
The annoying parts, fixed
We read the reviews of the dual-subtitle extensions people already use and started with what they complained about most.
Free does almost everything
Pro removes two limits: AI explanations and saved words. Everything else is free, with no time limit.
| Key | Feature | Plan |
|---|---|---|
| ASD | Previous line, replay, next lineStep through a video one sentence at a time. | FREE |
| Q | Auto-pauseAfter every line, or only after lines with words you don't know yet. | FREE |
| R | Loop a lineHear it until it sticks. | FREE |
| W | Hide the translationSwitch to the original line only. | FREE |
| E | Transcript beside the videoClick any line to jump there. Filter to lines with new words. | FREE |
| · | Words colored by what you knowSee how much of a video you understand before you press play. | FREE |
| · | Flashcards with spaced repetitionEach card keeps its sentence, translation and a link to the exact second. | FREE |
| · | Anki export and AnkiConnectDownload a file Anki imports as-is, or send cards straight in. | FREE |
| · | AI ExplainWhat a word or phrase means in this exact line: slang, tone, grammar. 5 a day free. | 5/DAY PRO |
| · | Saved words200 on the free plan. | 200 PRO |
Start free. Upgrade if you want more.
Pro has a 7-day free trial and you can cancel from the extension anytime.
- Dual subtitles on YouTube
- Click words, drag across phrases
- Word colors, auto-pause, loop, transcript
- Flashcards and Anki export
- 200 saved words, 5 AI explanations a day
- Everything in Free
- Unlimited AI explanations
- Unlimited saved words
- 7-day free trial
Payments by Stripe. Prices in USD.
Before you install
Which videos does it work on?
YouTube videos that have subtitles, including auto-generated ones. If the video has no subtitles in the language you're learning, Doublet uses YouTube's own machine translation of the subtitles it does have. If a video has none at all, you get a clear message instead of a spinner.
Do I need an account?
No. Install it and press play. Saved words and flashcards are stored in your browser. Pro is linked to your install, not an email address.
Which languages?
Any language YouTube has subtitles for. Word lookups use Wiktionary, which is strongest for widely studied languages like Spanish, French, German, Japanese, Korean, Chinese and Portuguese.
Is this a Language Reactor alternative?
It does the same core job on YouTube (two subtitle lines and word lookups) and adds phrase selection, word colors, flashcards and auto-pause on new words. It doesn't support Netflix.
How do I cancel Pro?
Open Doublet, click Manage subscription, and cancel in the Stripe page that opens. You keep Pro until the end of the period you paid for.
What happens to my words if I uninstall?
They're deleted with the extension, because they only live in your browser. Download them for Anki first if you want to keep them.
Your words stay with you
Doublet shows dual subtitles on YouTube to help you learn languages. This policy explains what it handles.
What stays on your computer
- Saved words and phrases, with their sentence, translation and video link. Stored in your browser. We never receive them.
- Your settings (languages, display options). Stored by Chrome, and synced to your own Google account if you use Chrome sync.
- Subtitles are read from the video you're watching, in your browser. They're never uploaded or stored by us.
What is sent, and to whom
- Dictionary lookups: the word you click is sent to Wiktionary (Wikimedia Foundation) to fetch a definition.
- AI explanations, only when you press Explain: the word or phrase, its subtitle line, the line's translation and your language codes go to our server, which asks Anthropic's API for an explanation and keeps a cached copy of the answer for up to 30 days. Anthropic's commercial API terms don't use this data for model training by default.
- Install ID: a random code created when you install Doublet, sent with explanation and billing requests so we can count free explanations and know if you have Pro. It isn't linked to your name or browsing.
- Payments are handled entirely by Stripe. We receive your Stripe customer and subscription IDs and subscription status, never your card number.
- Anki: "Send to Anki" talks only to Anki on your own computer.
What we don't do
- We don't collect your YouTube watch history, sell data, show ads, or use your data for anything other than the features above (Chrome Web Store Limited Use policy).
- Doublet is not intended for children under 13.
Your choices
- Delete saved words anytime in the extension, or uninstall to remove everything stored locally.
- To have your install ID and subscription record deleted from our server, email support@getdoublet.com.
Last updated October 2026.