Privacy Policy
Helios is a language-learning extension that runs in your browser. This page explains, in plain terms, exactly what it stores and the few things it sends out.
Last updated: 14 September 2026
No account
There is no sign-up and no Helios server holding your learning data.
Saved on device
Your vocabulary, stats and settings live in your browser's local storage.
No tracking
No analytics, no telemetry, no ad networks, no tracking pixels.
What stays on your device
Helios saves the following in your browser's extension storage. None of it is sent to Helios, and none of it is synced to any account.
- Vocabulary and progress: saved words, words marked known or ignored, lookup counts, and daily and session totals.
- Preferences: your target and native language, popup theme and font size, activation key, hotkeys, and popup behaviour.
- Video and subtitle settings: subtitle size and visibility, preferred subtitle tracks, and player hotkeys.
- Anki configuration: your chosen deck, note type, field mappings and tags, plus counts of cards created.
- Install details: install date, extension version, and whether you finished onboarding.
Dictionaries are downloaded once and then stored on your device, so looking up a word does not require a network request.
What leaves your device
Helios is built to work offline, but a few features genuinely do make network requests. Here is the complete list.
| Feature | Goes to | What is sent |
|---|---|---|
| Dictionary download | Helios file storage (Cloudflare R2) | The language pair you picked, e.g. Chinese → English. No words, no page data. |
| Word audio (when you press play) | ChinesePod101, Google Translate | The single word or phrase you asked to hear. |
| Word audio via Forvo (optional) | Forvo | The word, but only if you supply your own Forvo API key. |
| Subtitles | The video site you are already on | An ordinary request for that video's subtitle track. |
| Anki cards | AnkiConnect on your own computer | Card text, and a screenshot or audio if you include one. Never leaves your machine. |
Worth being clear about
When you press play on a word's pronunciation, that word is sent to an outside audio provider so it can return a recording. Those providers are not run by Helios and handle the request under their own privacy policies. Audio only ever fires when you press the button, never automatically, and never for words you merely hover over. If you would rather nothing left your device at all, simply do not use the audio button; every other feature works without it.
Some devices can also speak a word using the voice built into your own operating system. That happens entirely on your computer and sends nothing.
What Helios never does
- Ask you to create an account, or collect your name, email address or phone number.
- Log your browsing history. Helios reads page text in your browser to find words to underline; that text is not sent anywhere.
- Run analytics, telemetry or crash reporting of any kind.
- Include advertising networks, tracking pixels or social media trackers.
- Sell, rent or share your information with anyone.
- Collect your IP address, location or device identifiers.
- Ask for payment or financial details.
Permissions, and why each one is needed
Browsers show a permission list when you install an extension. Here is what each one is actually for.
- Storage: to keep your vocabulary and settings on your device.
- Active tab and tabs: to know which page you are reading, and to take a screenshot when you ask for one on an Anki card.
- Scripting: to place the dictionary popup onto the page.
- Offscreen: to keep the dictionary loaded in memory so lookups stay fast.
- Alarms: to reset your daily lookup counter.
- Access to websites: so the dictionary works on whichever page you choose to read.
The website access permission looks broad because the browser has no way to say “any page the user points this at.” It is what lets the popup appear on any site you are reading. It does not mean those pages are sent anywhere.
Anki integration
If you use Anki, Helios talks to the AnkiConnect add-on at 127.0.0.1:8765. That address is your own computer. Cards, screenshots and audio are handed straight to the copy of Anki running locally, and do not travel over the internet or through Helios.
Your controls
- Remove individual words from your vocabulary at any time in the extension.
- Turn Helios off for a while using the toggle in the extension popup.
- Clear everything by removing the extension's storage in your browser settings.
- Uninstall the extension, which deletes its stored data along with it.
Because nothing is held on a Helios server, removing it from your device removes it completely. There is no copy elsewhere for us to delete.
Children's privacy
Helios is not directed at children under 13 and we do not knowingly collect information from them. Since the extension collects no personal information from anyone, there is no children's data for us to hold. If you are a parent with a question, please get in touch using the form linked below.
Your rights
Privacy laws such as the GDPR and the CCPA give you rights to see, correct, export or delete the personal information a company holds about you.
Helios does not operate accounts and does not collect personal information, so there is no profile on our side to produce or erase. The data the extension creates sits on your own device, under your direct control, and you can inspect or delete it at any time using the steps above. If you believe we hold information about you and want to ask about it, contact us and we will respond.
Changes to this policy
If Helios gains a feature that changes what is stored or sent, this page will be updated and the date at the top will change with it. Material changes will be described here rather than quietly folded in.
Contact
Questions about any of the above are welcome, including the parts you think are wrong.