公开视频的共享处理：如果一个视频经 YouTube Data API 确认是公开视频，而另一位用户正好也在请求这个视频，你们的请求会合并成一次处理，这次处理使用发起者的登录态。因此，你的登录态可能被用于一次处理，而这次处理生成的机器字幕也会提供给同时请求这个公开视频的其他用户。你的登录态和个人数据不会提供给他们。非公开视频（不公开列出、私享、会员专属、有年龄或地区限制，或无法确认公开的视频）只为发起请求的用户单独处理。
This policy explains what data the Bunmyaku (文脈) website at getbunmyaku.com and its Chrome extension “Bunmyaku Sign-in Sync” (Chinese name “Bunmyaku 登录态同步”) collect, why, who processes it, how long it is kept, and how you can revoke and delete it. The Chinese and English versions have the same content.
1. Who we are
Bunmyaku is a website for learning Japanese from YouTube videos: you submit a video link, the service generates subtitles, translations and explanations for you, and you can save sentences, write notes, and practise with flashcards and exercises. It is run by an individual developer and registration is currently by invitation only.
Contact: jiajie.zhou95@gmail.com. Send any question about this policy or your data, and any revocation or deletion request, to this address.
Bunmyaku is not affiliated with, endorsed by or sponsored by YouTube or Google.
2. Key points
Only after you click the toolbar icon on getbunmyaku.com, read the notice and click “Agree and sync” does the extension read all your youtube.com cookies (including sign-in cookies) and upload them to Bunmyaku's server, where they are stored encrypted.
The server uses this sign-in only when you submit a video, to temporarily retrieve that video's audio and frames and generate subtitles for you. For videos submitted on getbunmyaku.com, the video and audio are deleted after processing, and so are the video screenshots, automatically after the processing job ends; the developer's test deployment handles media differently, see section 6.
Because the server uses your own sign-in to retrieve the videos you submit, it can also retrieve videos that are not public but that your own YouTube account can already watch (unlisted, members-only or age-restricted); subtitles made from those videos stay private to you and are not given to other users (see section 4).
You never receive a video file, and Bunmyaku has no video download feature. The output is subtitle text, timestamps, translations and learning notes; playback happens only in YouTube's official embedded player.
Your sign-in is kept for at most 7 days, and you can revoke it at any time; revoking deletes it from the server immediately.
We do not sell any data or use it for advertising, and neither the website nor the extension contains analytics or advertising trackers.
3. What the Chrome extension collects, and when
Some YouTube videos can only be retrieved while signed in. The extension's single purpose is to let a signed-in Bunmyaku user link their own YouTube sign-in to their own Bunmyaku account, and to revoke that link at any time.
When: When you click the extension's toolbar icon on a getbunmyaku.com page, a panel appears at the bottom right of the page, and it first explains what will happen. The panel also opens by itself when the site reports that your synced sign-in has expired; even then nothing is read until you click the toolbar icon and then “Agree and sync”. The extension reads no cookies before you click “Agree and sync”. Each click on the icon grants a one-time permission that expires after 15 seconds and applies only to that tab.
What it reads: All cookies your browser holds for youtube.com and its subdomains, including sign-in cookies (for example SID, SAPISID, __Secure-3PSID): their names, values, domains, paths, expiry times and security flags, formatted as cookies.txt text. These cookies let the server act as your signed-in YouTube account; it uses them only to fetch media for videos you submit (see section 4). If you prefer not to link your main account, consider syncing from a Chrome profile signed in to a separate YouTube account. At least one sign-in cookie must be present, otherwise nothing is sent. The extension does not read cookies of any other site, your browsing history, page content or any other data.
Where it goes: The extension's script on the getbunmyaku.com page sends this text once, over HTTPS, to the account endpoint of the same site (getbunmyaku.com), together with your Bunmyaku sign-in. The server requires you to be signed in with a verified email address.
The extension itself: The extension's background script makes no network requests, the extension stores no cookies locally, and it contains no remote code and no analytics or tracking code. Its script runs only on getbunmyaku.com, never on YouTube or any other site. Chrome shows that the extension has access to youtube.com (to read cookies) and getbunmyaku.com (where the panel runs); the extension never reads getbunmyaku.com's cookies.
Status and revoking: The panel asks the server for the current status (whether a sign-in is stored, the number of cookies, when it was synced and when it expires). Clicking “Revoke and delete” makes the server delete your stored sign-in immediately.
4. How the server uses your YouTube sign-in
Only when you submit a video on Bunmyaku does the processing job for that video decrypt your sign-in and use it to request that video's media (audio and frames), its available caption tracks and its basic information from YouTube, in order to generate subtitles for you. Your sign-in is not used for anything else: not to browse or act on YouTube as you, not to read your YouTube account data, and not for videos you did not submit.
Because the retrieval uses your sign-in, the server can retrieve any video your own YouTube account can already watch, including unlisted, members-only or age-restricted videos. Such non-public videos are processed for you alone, and the subtitles made from them stay private to you and are not given to other users (see the next paragraph).
The decrypted cookies exist only as a temporary file for the duration of that retrieval, readable only by the processing program, and the file is deleted as soon as the retrieval finishes. Server logs redact cookies and never record their values.
Your sign-in is sent only to YouTube, as part of those retrieval requests. We never send it to DeepSeek, Cloudflare Workers AI, Google Cloud Run, the email provider or any other third party.
Shared processing of public videos: if the YouTube Data API confirms that a video is public and another user requests the same video at the same time, the requests are combined into a single processing run that uses the sign-in of the user who started it. Your sign-in may therefore be used for a run whose machine subtitles are also delivered to other users who requested the same public video. Your sign-in and personal data are never given to them. Non-public videos (unlisted, private, members-only, age- or region-restricted, or not confirmed as public) are processed only for the user who requested them.
The operator: the developer has administrative access to the server infrastructure and the encryption key, and could technically decrypt it. Apart from the automatic use when you submit a video, the developer does not view or use your sign-in; the test deployment's automated test path uses only the sign-in of the developer's own account.
Test deployment: the developer also runs a test copy of Bunmyaku (bunmyaku-japanese-learning-staging.jiajie-zhou95.workers.dev) that shares the account database and private storage with getbunmyaku.com, so the same accounts can sign in there and your encrypted sign-in is in the same database. It is meant for the developer's testing and handles media differently from getbunmyaku.com; see section 6. Please use Bunmyaku at getbunmyaku.com.
5. How your sign-in is stored and deleted
Encryption: The server encrypts it with AES-256-GCM before storing it in the database; the key is kept separately as a server secret. Each record is bound to your account and cannot be decrypted under another account. The database holds only the ciphertext, the cookie count and timestamps, never the plain text. Each account has at most one stored copy, and syncing again replaces it.
How long: Until the earlier of: the expiry time of your YouTube sign-in cookies, or 7 days after syncing. Expired records are deleted automatically by a scheduled task that runs every 5 minutes.
Revoking: Click “Revoke and delete” in the panel and the server deletes your stored sign-in immediately.
Deleting your account: Deleting your Bunmyaku account also deletes your stored sign-in.
Uninstalling the extension: Uninstalling the extension does not by itself delete the copy stored on the server. To delete it immediately, revoke before uninstalling; otherwise it is deleted automatically at the expiry described above.
6. Video, audio and screenshots
To generate subtitles, Bunmyaku's server temporarily retrieves the video's audio and frames for the requesting user and processes them: the audio is used for speech recognition, and still images taken from the video (a small number of whole frames used to locate the subtitles, otherwise the horizontal band containing them) are used to read the subtitles shown on screen. The first four items below describe getbunmyaku.com; the developer's test deployment is covered in the last item.
Video and audio: Kept only in the processing container's temporary storage and deleted after processing; if they are not released normally, they are deleted after 3 hours of inactivity.
Video screenshots: Video screenshots taken to read on-screen subtitles are stored privately and deleted automatically after the processing job ends, normally within about 30 minutes; screenshots from jobs that stop without finishing are deleted within about 2 days. The recognized subtitle text is kept as part of your subtitles. The raw recognition result files are deleted together with the screenshots.
What you receive: You never receive a video file, and Bunmyaku has no video download feature. The output is subtitle text, timestamps, translations and learning notes.
Playback: When you watch a video in Bunmyaku, playback happens only in YouTube's official embedded player, which your browser loads directly from YouTube; YouTube's and Google's privacy policies apply to it.
Test deployment: Videos submitted on the developer's test deployment described in section 4 are processed with an older method: the video file and its audio are kept in private storage, currently without automatic deletion, and images from the video are sent to DeepSeek to recognize the subtitle text.
7. Data the website collects
Account: Your email address, name, password (stored as a hash by the authentication library, never in plain text), email verification status and creation time. Email verification and password reset links are valid for 1 hour and are also stored hashed.
Sign-in state: When you sign in, the website sets one essential sign-in cookie (__Secure-bunmyaku.session_token: HTTPS only, not readable by scripts, valid for 7 days and renewed daily while you use it). The server's sign-in records include your IP address and browser identifier (User-Agent).
Learning data: The video links you submit and their processing history, saved sentences and tags, notes, follow-up conversations, manual subtitle corrections, practice and flashcard results, learning progress, playback positions, preferences, and usage and quota records.
Subtitles: Subtitles generated for you are stored linked to your account. For videos the YouTube Data API confirms as public, and that are also confirmed public when retrieved, the machine subtitles are cached and reused for other users who request the same video; these shared subtitles contain no sign-in information or personal data. Your manual corrections, notes and learning records always remain yours alone.
IP address: Used for account security and rate limiting, for example at most 5 sign-in syncs per minute from one IP address, and abuse limits on signing in and deleting accounts.
Server logs: Operational events (for example processing stage, video ID, timings and errors), used to run the service and fix problems. Logs do not record passwords, cookies or sign-in tokens; such values are redacted.
No tracking: The website contains no analytics, advertising or tracking code and sets no advertising cookies. Some pages load fonts from Google Fonts, which lets Google see your IP address and browser information.
8. How we use data
We use data only to provide and protect Bunmyaku: to generate subtitles, translations and explanations, to store your learning records, to let you continue on other devices, to send verification and password reset emails, to prevent abuse, and to fix problems.
We do not sell data, do not use it for advertising or profiling, do not use it for purposes unrelated to the learning service, and do not use your data to train models.
9. Service providers
We use the following providers to run Bunmyaku. Each receives only the data needed for its job, and they may process data outside your country or region.
Cloudflare: Hosts the website and all server-side data: Workers, the D1 database, private R2 storage, Containers (the processing container), Workflows and Queues; and Workers AI Whisper speech recognition, which receives audio segments of the video.
Google Cloud Run: Receives still frames from the video (whole frames or the subtitle band), plus processing details such as frame numbers and timestamps, and returns the recognized text. It does not receive your account, email address, video ID or cookies.
DeepSeek: Receives subtitle text (for translation); the sentence you select with its context, the video title, and your questions and conversation (for explanations, follow-ups and note summaries); and a few whole video frames, to locate where subtitles appear; on the developer's test deployment, also images from the video, to recognize the subtitle text. It does not receive your email address, password or YouTube sign-in.
YouTube / Google: The server requests the media of the videos you submit from YouTube (with your sign-in, if you synced it); the YouTube Data API receives only the video ID, to check whether a video is public; YouTube oEmbed receives the video link, to look up its title. Playback uses YouTube's official embedded player.
Resend: Sends account emails (email verification, password reset) and receives your email address and the link in the email.
Google Fonts: Serves fonts for some pages.
10. Chrome Web Store User Data Policy
Bunmyaku's use of information received from its Chrome extension adheres to the Chrome Web Store User Data Policy, including the Limited Use requirements.
Data obtained by the extension is used only for the single purpose described above: retrieving media of the videos you submit, generating learning subtitles for you, and letting you revoke the link.
It is sent to YouTube only as necessary for that purpose, or disclosed where required by law; it is never sold or transferred to anyone else.
It is not used for personalized advertising, retargeting or any other advertising, or to determine creditworthiness or for lending.
No person reads it unless you explicitly agree, for security purposes such as investigating abuse, or where required by law.
11. Retention at a glance
YouTube sign-in: Until your sign-in cookies expire or 7 days after syncing, whichever is earlier; deleted immediately when you revoke it or delete your account.
Temporary cookie file during processing: Deleted as soon as the retrieval finishes.
Video and audio (getbunmyaku.com): Deleted after processing; at most 3 hours of inactivity.
Video screenshots and raw recognition result files (getbunmyaku.com): Deleted automatically after the processing job ends, normally within about 30 minutes; for jobs that stop without finishing, within about 2 days.
Video and audio files on the developer's test deployment: Kept in private storage; currently no automatic deletion.
Recognized subtitle text and processing records: Kept as part of the subtitles and job records.
Your subtitles, learning data and account: Kept until you delete them or delete your account.
Shared machine subtitles of public videos: Kept for reuse; they contain no personal data and are not deleted when an individual account is deleted.
After account deletion: Your account, learning data, private subtitles and stored sign-in are deleted; private subtitle files are removed asynchronously by a background task. Records of finished processing jobs are kept with your account identifier removed; audit records of administrative actions may be kept.
12. Your choices and rights
Revoke your sign-in: At any time, click “Revoke and delete” in the extension panel.
Export: In the learning workspace you can export saved sentences and cards as CSV, Anki or JSON. For a copy of other data, email us.
Correct: You can correct subtitles manually, edit notes and change your password.
Delete your account: On the account page, enter your password to permanently delete your account and learning data.
Other requests: For other requests to access, correct or delete data, email jiajie.zhou95@gmail.com.
13. Security
All traffic uses HTTPS. Your YouTube sign-in is stored encrypted; every access to private data is checked against the owning account; passwords and one-time tokens are stored as hashes; private storage is not publicly accessible; and sensitive values are redacted from logs. No system can be guaranteed perfectly secure, and Bunmyaku holds no third-party security certification or audit. If you find a security issue, please contact us.
14. Children
Bunmyaku is not directed at children under 13, and we do not knowingly collect personal information from children. If you believe a child has given us personal information, contact us and we will delete it.
15. Changes to this policy
We will post any change to this policy on this page and update the effective date. If we change how the extension uses your data, we will update this policy and the notice in the extension panel before the change takes effect.