Language immersion extension · Fluidity family
Learn languages from what you watch and read.
Interactive subtitles, word tools on the original webpage, a saved reading library and local guest review. Submersion connects the language you encounter with the vocabulary you keep.
Watch it. Read it. Understand it. Remember it.
- Free
- Netflix and YouTube
- Webpages and reading library
- Shared vocabulary, local source context
Submersion
haはeiga映画woをmi見niにikanai行かない？
Want to go see a movie today?
One extension for what you watch and read
Watch
Explore Netflix and YouTube captions, local video files, and supported HTML5 players with interactive Study and Gloss tracks.
Webpages
Use Submerge this page to explore words in supported news articles, blogs, forums and online stories without leaving the original website.
Reader
Save multiple texts, organize collections, search documents, resume reading and listen with sentence-by-sentence text-to-speech.
Vocabulary
Collect vocabulary from videos, webpages and Reader, track familiarity, and export words with source context.
Review
Guests can use local spaced repetition without an account. Signed-in review is permission-gated and is not currently activated in production.
How it fits the watch
Nothing to set up mid-scene.
-
1
Load it and pin it
Drop the folder into
chrome://extensions, then open a title with captions already turned on. -
2
Read both lines
The study language sits on the player with the gloss underneath. Click any word for its reading and meaning.
-
3
Walk the dialogue
Z goes back a line, X replays it, V jumps ahead. Space still belongs to Netflix and YouTube.
Features
What you get
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Meaning on click, in the scene
Semantide for Japanese, Chinese, French, and English; a translation fallback for everything else. The card shows the reading, the senses, and the other lines in this title where the word turns up — right-click to set Unseen / Studying / Solid / Skip.
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Colour the words you already know
Sign in and captions pick out the words you know in Fluidity. They recede, so the line you are still learning is what you look at.
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Two official tracks
The captions your account already has. If the title has no gloss track, Submersion can fill in an automatic one.
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Transcript, frequency, kept
Search the running transcript, rank every word in this title by how often it appears, and keep the lines worth coming back to.
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Cover until you look
Blur the study line and uncover it on hover, so you hear it before you read it. U reveals the whole sentence.
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Stop at the end of a line
Optional, and toggled with P while you watch. Speed lives on − and =.
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Beside the player, not over it
Dock the panel and the video shrinks to make room, so the transcript never sits on top of the shot you are watching.
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Saved texts, read-along and review
Save documents, resume reading and listen sentence by sentence. Keep words with their source context, export CSV or Anki TSV, and review locally as a guest. Signed-in review awaits additional Fluidity authorization.
Keys
Six keys, and one of them is Netflix's.
- Z last line
- X this line again
- V upcoming line
- P pause each line
- U unblur
- B keep this line
- − = speed
- Space play / stop, still the host's
Plainly
What it doesn't do.
- It can't add languages you don't have. Submersion reads the caption tracks Netflix and YouTube hand your account. If a title ships without the language you want, nothing here conjures it.
- It doesn't upload what you watch. When signed in, Fluidity synchronizes canonical word identity, enrollment, learner decks and knowledge through its API. Local account caches support offline use. Looking up or hovering a word sends no learning evidence. Page text, captions, Reader imports, source sentences and URLs, browsing state and preferences stay in Submersion on this device. Dictionary and translation lookups send the requested text to their services.
- It isn't a course. Sign in with your Fluidity family account to use shared saved words, decks and knowledge. Keeping a word enrolls it; it does not prove mastery. The Fluidity app is not required.
Install
Three steps, about a minute.
Free. Submersion is an unpacked Chrome extension while we get a store listing together. Chrome 120 or newer, on desktop.
Study and Gloss can each be Japanese, English, Korean, Chinese (Simplified), Chinese (Traditional), Spanish, French, German, Portuguese, Italian, Russian, Arabic, Hindi, Thai, Vietnamese, Turkish, Polish, Dutch, Swedish, Indonesian, Ukrainian, Czech, Romanian, Hungarian, Greek, Hebrew, Finnish, Danish, Norwegian, Malay, or Filipino. Click-for-meaning uses Semantide for Japanese, Chinese, French, and English, and a translation for every other language in that list.
- Open
chrome://extensionsand turn on Developer mode. - Choose Load unpacked, and pick the folder that holds
manifest.json. - Pin Submersion. In the popup, set Study and Gloss to caption languages the title actually has — Japanese and English are the defaults — then play it with those captions on.
After you update the folder, reload the extension and hard-refresh the player. Overlay scripts do not pick up a save on their own.