Privacy policy
This policy explains how Band Stem Mixer (https://ktkwmr.com/bandstemmixer/, "this site") handles information. In short: your song is separated on your device and never uploaded. To do that, your browser downloads an AI model and a library from external services.
1. What you do in the app
The audio file you choose is read, separated into parts by the AI model, and played only in your browser. The file, the separated parts, and their names are never sent to our server or to anyone else. Saving a part or a mix as an MP3 file only saves it on your device. The app does not use the microphone. This site has no accounts, and we do not ask for your name, email address, or other personal information.
2. Data saved in your browser
The following data is saved in your browser's storage on your device. It is not sent to us.
- The AI model: the model file (about 170 MB) downloaded the first time you separate a song, so it is not downloaded again.
- Mixer settings: the level and mute of each part, the master volume, and whether the GPU is used.
- App files: the pages and files of this site and the ONNX Runtime library, so the app works offline.
Your songs and the separated parts are not saved in the browser; they are gone when you close or reload the page. To delete the data above, use “Reset mixer” and ⚙ → “Delete the AI model” in the app, or clear this site's data (site data, cookies, and storage for ktkwmr.com) in your browser settings.
3. Information sent to external services
When you use this site, your browser sends information to the following services. This list also serves as the notice of external transmission required under Japan's Telecommunications Business Act.
| Service (operator) | When | Information sent | Purpose |
|---|---|---|---|
| Cloudflare (Cloudflare, Inc.) | Every page and file request | IP address, browser information (user agent), requested URL, date and time | Hosting this site, security, and access logs for operation |
| Cloudflare Web Analytics (Cloudflare, Inc.) | Every page view | IP address, browser information (user agent), the URL of the page, referrer, page load time. No cookies are used. | Counting page views (see "Analytics" below) |
| Hugging Face (Hugging Face, Inc.) | The first time you separate a song (until the model is saved in your browser) | IP address, browser information (user agent), the URL of the model file, date and time. Nothing about your song is sent. | Downloading the AI model (Demucs htdemucs) |
| jsDelivr (a CDN run by Prospect One and its partners) | When you separate a song (until the library is saved in your browser) | IP address, browser information (user agent), the URL of the library file, the page that requested it (referrer), date and time | Downloading ONNX Runtime Web, the library that runs the AI model, demucs-web, which prepares the audio for it, and (when you save a file) lamejs, which makes the MP3 |
4. Cookies and advertising
This site does not set cookies and does not show ads. If we add ads in the future, we will update this policy before they are shown.
5. Analytics
To see how many people use this site, we use Cloudflare Web Analytics. It counts page views without cookies and without identifying or tracking individual visitors across sites. We do not use Google Analytics.
6. Sharing with third parties
We do not collect personal information that identifies you, and we do not sell or provide it to third parties, except where required by law.
7. Contact
For questions about this policy, please open an issue on GitHub Issues. See about this site for the operator.
8. Changes to this policy
We may update this policy when the site changes, for example when we add or remove a service. The updated policy applies from the time it is posted on this page.
Effective: October 28, 2026