Fluidity family · Chrome
Privacy Policy
Last updated October 9, 2026
Submersion is a Chrome extension in the Fluidity family, operated by Kawaki Technologies LLC (“Kawaki”, “we”, “us”). This policy describes how Submersion handles information when you use the extension, this website (submersion.usefluidity.com), and related pages such as Support.
Fluidity supplies shared learner vocabulary and knowledge. The Fluidity app is not required to use Submersion.
Summary
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.
If you choose Submerge this page, Submersion reads that page’s text inside your browser to find words in your study language and to show which ones you know. The page is not uploaded, logged, or kept. As everywhere else, clicking a word sends that word to the dictionary services below, and Translate sentence sends that one sentence.
Information the extension handles
On your device, Submersion may store:
- Settings — study/gloss languages, interface language, dock, romaji, pause-each-line, and similar preferences (
lyricaSettingsin Chrome storage). - Kept words include local source sentences, page titles and URLs. Signed-in vocabulary, decks and knowledge are cached from Fluidity. Legacy originals are preserved locally.
- Local video — selected video and subtitle files are opened on this device without uploading them. Explicitly kept frames and audio clips are saved in account-scoped IndexedDB (
submersion-media). The full video is not saved; reopen the original file to return to a kept line. You can delete saved clips on the Local video or Kept page. - Reader library — imported pages, text files and EPUB text stay in account-scoped IndexedDB (
submersion-library), with original source, collections, chapter positions and resume progress. Translation sends one sentence only on click. - Per-site activation preferences and local page-reading state. Browsing history is not synchronized to Fluidity.
- Firebase session tokens, an account-bound Fluidity binding and account-scoped offline caches. Sign-out clears the active session and shared view.
This website may store a theme preference and interface language (submersion-site-theme, submersion-ui-lang) in your browser’s localStorage. We do not set advertising cookies on this site.
Information sent off the device
The services below receive the information needed for sign-in, shared learning state, dictionary lookups or translation. Source URLs and browsing history are not sent to Fluidity.
| Service | When | What is sent |
|---|---|---|
| Semantide (semantide.com) | You click a Japanese, Chinese, French, or English word, or a pronunciation lookup needs a dictionary fallback | The word |
| Tubonics, Morphanese, Semantide | You choose a Fluidity family link on a word card | The word, or the caption line for Morphanese, in that site’s address |
| Google Translate API (translate.googleapis.com) | Automatic pronunciation lookups while readings are displayed, non-Japanese lookup, or a missing gloss track | The word or caption line |
| Google Translate API (translate.googleapis.com) | You choose Translate sentence on a word card from a submerged page | That one sentence |
| MyMemory (api.mymemory.translated.net) | Fallback if Google Translate is unavailable | The word or caption line |
| dictionaryapi.dev | You click an English word | The word |
| Google Identity / Firebase Auth | You choose “Continue with Google” in the popup or on /auth | Account identity and Firebase authentication tokens. The trusted Submersion broker exchanges your ID token for account-bound Fluidity permissions. |
| Fluidity API | While signed in, background synchronization | Account identity and the shared enrollment, deck and knowledge records needed for your local cache |
| Fluidity API | You keep a word or explicitly change its learner status | The canonical word ID and enrollment, known, excluded, paused or reset command; no source URL, sentence or fabricated review |
| Fluidity API | You create, rename or delete a deck, or change its words | Shared deck ID, name and canonical word membership |
| Fluidity word registry | A saved word needs a canonical identity | Word and language, or a verified dictionary reference; ambiguous matches remain unresolved |
Netflix and YouTube caption requests stay in your logged-in session. Submersion asks those sites (and their caption hosts) for tracks you can already play. We do not bypass logins, DRM, or region locks, and we do not redistribute caption files.
Vocabulary review and speech
Guest grades and due dates are stored only on this device and are never imported or merged into Fluidity on sign-in. Authorized signed-in grades use Fluidity’s existing schedule and evidence pipeline; source context stays local. Signed-in review is currently unavailable in production pending review permission and producer approval. Browser text-to-speech uses available voices; some voices may use the browser or operating system provider’s online service. Fonts are bundled and no font CDN is contacted.
How we use information
- Draw two caption tracks and meanings on the player.
- Remember settings and the words you keep.
- Open imported text in Submersion Reader when you ask.
- Synchronize your saved words and learner decks through Fluidity.
- Answer support mail if you write to us.
- If you tap Share, your browser opens that network with the public Submersion link (and, if you share a line, that line’s text). We do not load share-tracker scripts.
- Show shared learner knowledge without treating a lookup as learning evidence.
- Find words on a page you submerge and show your learner state on them, in your browser.
We do not sell your information. We do not use Submersion data for ads.
Chrome Web Store Limited Use
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.
Text from a page you submerge is used only on your computer to find words and show your learner state. It is not sent to Kawaki, sold, or kept, apart from a word or sentence you choose to keep.
Permissions
- storage — settings, kept words, imported reader text, and (if you sign in) the Fluidity session cache.
- identity — open Google sign-in and return you to the extension.
- contextMenus — the “Submerge this page”, “Open this page in Submersion Reader”, and “Read selection in Submersion Reader” items.
- scripting and activeTab — when you choose Submerge this page (popup, right-click, or Alt+Shift+S), load Submersion’s page reader into that one tab; when you choose a Reader item, read that tab’s text. Nothing runs on tabs you have not acted on.
- Optional access to one site at a time — only if you switch on Always on for a site. Chrome asks for that site alone; turning the switch off, or removing the site in Chrome’s settings, takes the access back.
- Host access to Netflix, YouTube, and their caption hosts — overlay the player and fetch caption documents already available to your session.
- Host access to Semantide, Google Translate, MyMemory, and dictionaryapi.dev — word meaning and invented glosses.
- submersion.usefluidity.com · securetoken.googleapis.com · api.usefluidity.com — The shared Firebase account signs you in; a trusted Submersion service exchanges your token for account-bound Fluidity permissions.
Retention and deletion
Local extension data stays until you delete it. To remove it: Chrome → Extensions → Submersion → Remove, or use “Clear data” on the extension’s details page. Uninstalling removes Submersion’s Chrome storage on that profile. Sign out in the popup to drop the Fluidity session on this computer; that does not delete your Fluidity account. This site’s theme preference can be cleared with the browser’s site data controls.
Sign-out clears the active shared view and session, and keeps account-scoped offline work for that same account. It does not delete your Fluidity account. Removing the extension removes its local data.
Children
Submersion is not directed at children under 13. We do not knowingly collect personal information from children.
Changes
If this policy changes, we will update the date above and post the new text at this URL. Material changes to how we handle data will also be noted on this site.
Contact
Kawaki Technologies LLC
Privacy and support:
hello@kawakitechnologies.com
More help: submersion.usefluidity.com/support