Duosub
Learn a language
every time you
watch YouTube.
Duosub shows two subtitles at once — the language you're learning and your own — right on the video. Stuck on a word? Click it.
Read both. Understand instantly.
No setup per video. Open anything with captions and Duosub reads YouTube's own subtitle track, translates it, and shows both lines in sync.
Pick two languages
The one you're learning, and your own. Or let Duosub follow the video's language automatically.
Play any video
Two subtitle lines appear over the player, perfectly synced — original on top, your language below.
Click to learn
Tap any word to look it up. Hover a line to pause and read at your own pace.
Built for daily practice.
The kind of thing you leave on every time you open YouTube.
Two subtitles, in sync
Original and translation together — choose which sits on top, and the size that reads best for you.
Click any word
Instant look-up on tap. Chinese and Japanese split per character, so single glyphs are clickable too.
Hover to pause
Move your cursor onto a line and the video waits while you read. Move away and it plays on.
38 caption languages
Powered by YouTube's own caption translation — Spanish, Japanese, Arabic, Hindi, Korean and many more.
13-language interface
The whole extension speaks your language, from the popup to the on-video labels.
Private by design
No account, no analytics, no servers. Subtitle fetches stay on youtube.com. Only storage permission.
🔒 Your watching stays yours.
Duosub does everything locally in your browser. It reads the captions YouTube already sends, translates them through YouTube's own translator, and draws the second line on screen. Nothing about what you watch is collected or sent anywhere.
- One permission:
storage, to remember your language settings. - No tracking, no analytics, no ads, no account.
- The only outbound click is Look up — it opens Google Translate, and only when you ask.
Start learning in two clicks.
Add Duosub, pick your two languages, and press play.
Works in Chrome, Edge, Brave and other Chromium browsers.