Privacy policy

Last updated: 7 October 2026

Waku is a browser extension that helps you learn Chinese from videos on YouTube and, if you turn them on, on Bilibili, WeTV, Netflix, iQIYI, Youku and Viki. This policy describes exactly what it does with data. It is short because Waku does very little.

The short version

Waku has no account, no server of ours, and no analytics. We do not receive your data, because there is nowhere for it to go. Everything Waku remembers about you is stored in your own browser.

Waku is not, however, entirely offline. Three services can receive data, and what each one gets is set out below. Two of the three can be switched off. The other video sites are only ever contacted if you turn Waku on for them, and Ko-fi only ever hears from you if you press a Support link yourself.

What Waku stores, and where

All of this lives in chrome.storage.local — your own browser, on your own computer. None of it is transmitted anywhere.

• The words you have saved to flashcards, and their review schedule
• The words you have marked as known
• Which words you have met before, and the titles of the videos you met them in
• Your daily activity counts, used to show a streak
• Your settings, including your chosen language and theme
• Whether the little "Support Waku" friend has appeared, when it last did, and whether you asked it not to return or told it you had left a tip. This is only so it does not nag you; it is never sent anywhere
• Caches, kept so the same work is not paid for twice: pronunciations, translated subtitle lines, translated dictionary definitions, and which videos have Chinese subtitles
• Your Gemini API key, if you choose to add one

Settings → Delete all my words erases all of the learning data and every cache. Removing the extension erases everything, including settings and the key.

What leaves your computer

YouTube — always

Waku asks YouTube whether the videos shown on your screen have Chinese subtitles, so it can mark the ones you can learn from. This sends those videos' identifiers and, as with any web request, your IP address. These requests are made without cookies, so they are not tied to your YouTube account.

Waku also reads the subtitle track that YouTube is already serving to the page you are watching. That happens inside your browser.

Other video sites — only if you turn them on

Waku works only on YouTube until you turn it on for another site from the toolbar popup or Settings. Chrome then asks you to allow that one site, and you can take the permission back at any time the same way. On a site you have turned on, while you watch:

• Bilibili: Waku asks Bilibili's own website for the video's details and subtitle list, as the Bilibili page itself does, so these requests carry your Bilibili login like the page's own requests. It also asks, without cookies, whether the videos shown on your screen have Chinese subtitles.
• WeTV, Netflix, iQIYI, Youku, Viki: Waku reads the list of subtitle tracks that the site's own player has already loaded, then downloads the Chinese track (and your translation language, if the site has it) from the site's own servers. The subtitle files are fetched without cookies. On Viki, the request for the episode's details goes to Viki's own website like the page's own. On Netflix, Waku also asks Netflix's player to offer the subtitles in one more format (WebVTT) alongside its own.

Nothing from these sites is sent anywhere else; the subtitles are used on your screen and the words you save stay in your browser.

Site icons in the popup

The toolbar popup shows each site's own icon, loaded from that site's servers when the popup opens, the same way a web page shows an image. No information about you is sent with these requests beyond what any image request from a web page carries (such as your IP address); Waku adds nothing to them and sends no referrer.

MyMemory — only as a fallback, and can be switched off

api.mymemory.translated.net is a free public translation service. Waku uses it only when Chrome's own on-device translator is not available on your computer.

When it is used, it receives:

• subtitle lines from the video you are watching, in order to translate them
• English dictionary definitions of words you look up, in order to translate them

No key, no account, and no identifier beyond your IP address is sent. MyMemory is a public translation memory: assume anything sent to it may be retained by them.

To avoid it entirely, open Settings and set the translation engine to Chrome built-in (which runs entirely on your computer and sends nothing anywhere) or to Off.

Google Gemini — only if you add your own key

generativelanguage.googleapis.com receives nothing at all unless you paste your own Gemini API key into Settings. Waku ships without a key.

If you add one, Gemini receives:

• words and the sentences they appeared in, when you ask for a grammar explanation
• words or lines you ask to have spoken aloud
• subtitle lines, only if you explicitly choose Gemini as your translation engine

Your key is stored on your computer, is read only by the extension's background worker, and is never placed into a YouTube page. Google may use free-tier API input to improve its products — that is Google's policy, not ours. Remove the key at any time with Remove key in Settings.

Ko-fi — only if you press Support

Settings, the toolbar popup and the little friend on YouTube each carry a "Support Waku" link to the maker's Ko-fi page. It is an ordinary link: it opens Ko-fi in a new tab and Waku sends nothing to Ko-fi. Waku does not handle, see or store any payment, and cannot tell whether you tipped; when you come back to the YouTube tab it simply asks, and remembers your answer on this computer. Once you are on Ko-fi's page, Ko-fi's own privacy policy applies. The little friend can be switched off in Settings.

What Waku never does

• It does not collect or transmit your browsing history.
• It does not read pages other than YouTube and the video sites you turn on yourself. Until you turn one on, its permissions are limited to https://www.youtube.com/*.
• It does not contain analytics, telemetry, advertising or tracking of any kind.
• It does not sell or share data with anyone, because it does not collect any.
• It does not download or run code from the internet.

Children

Waku is a language-learning tool with no social features, no accounts and no data collection. It is not directed at children under 13 and collects nothing from anyone.

Changes

If this policy changes, the updated version will ship with the extension and the date at the top will change.

Contact

Questions about this policy can be sent to the address listed on the extension's Chrome Web Store listing.