Stemify — Privacy Policy

1. Overview

Stemify ("the App", "we", "us") is a music stem separation app for Android. This Privacy Policy describes what information may be collected when you use Stemify, how it may be used, who it may be shared with, and your choices.

Stemify uses third-party services — Google AdMob and Google UMP for advertising and consent, Firebase Analytics and Mixpanel for usage insights, Firebase Crashlytics and Firebase Performance Monitoring for diagnostics, and Firebase Cloud Messaging for push notifications. These services may process limited device and usage data as described below.

2. How the app works

Here is the full flow of how Stemify works from the moment you open it:

• Import: You select an audio or video file (MP3, WAV, FLAC, AAC, M4A, MP4) from your device using the system file picker. The file path is read locally — no upload occurs.
• Decoding: The audio is decoded to raw PCM samples entirely in your device's memory using Android's MediaCodec hardware decoder.
• AI model inference: The decoded audio is processed by an on-device ONNX model (HTDemucs by Meta AI) running via ONNX Runtime. The model runs entirely offline on your device's CPU/NPU. Your audio never leaves the device.
• Mixer screen: The separated stems (vocals and instrumental) are loaded into a two-track mixer. You can independently control each stem's volume, mute, or solo tracks.
• Download: You can export individual stems or all stems as WAV files directly to your device's Music folder.

Banner ads are displayed on key screens. Interstitial and optional rewarded ads may be shown at specific moments, depending on ad availability, eligibility, and consent choices.

3. What data is collected — summary

4. Your audio files

When you import a song, Stemify reads the audio file directly from your device storage. The file is loaded into RAM, processed entirely on-device, and the resulting stems are written back to your local Music folder. At no point is any audio data transmitted over the internet or stored on any server operated by us or any third party.

The on-device AI model (HTDemucs) is embedded in the app itself. It runs locally using ONNX Runtime and requires no internet connection to function. Even if your device is in airplane mode, Stemify will process your song without any degradation in quality or functionality.

5. Advertising (Google AdMob)

Stemify is free to use and is supported by advertising provided by Google AdMob, a service operated by Google LLC. AdMob displays three ad formats in Stemify:

• Banner ads — displayed at the bottom of the home screen and processing screen while you wait for your song to be processed.
• Interstitial ads — a full-screen ad that may appear at navigation checkpoints (for example after processing). These are frequency-capped and currently limited to no more than once every ~3 minutes, subject to ad inventory and product changes.
• Rewarded ads — optional ads that may be offered before certain export actions. You choose whether to watch, and a reward outcome event may be recorded.

To serve relevant ads, AdMob may collect and use:

• Your device's advertising ID (a resettable identifier)
• Approximate location (country/region level, derived from IP address)
• Device model, OS version, and app version
• Ad interaction data (impressions, taps, rewarded completion events)

AdMob may serve personalised ads based on your interests, or contextual ads if you have opted out of personalisation. Stemify also uses Google's User Messaging Platform (UMP) to request and manage ad consent where required, and may show an in-app "Ad privacy options" control for supported regions.

Ad consent controls in Stemify apply to advertising. They do not automatically disable all analytics, crash diagnostics, or performance telemetry from third-party SDKs.

You can manage your ad preferences at any time:

• On your Android device go to Settings → Privacy → Ads
• Tap "Reset advertising ID" to get a fresh ID
• Enable "Opt out of Ads Personalisation" to receive contextual ads only

AdMob's data practices are governed by the Google Privacy Policy. We do not receive raw ad-tech profiles and cannot control third-party processing beyond the settings and consent tools made available by Google.

6. Analytics (Firebase Analytics + Mixpanel)

Stemify uses Firebase Analytics (by Google) and Mixpanel to collect product usage statistics that help us understand app usage and improve features.

These analytics services may collect:

• Screen views and navigation patterns (e.g. which screens are visited)
• Feature usage events (e.g. "processing started", "stems exported")
• Session duration and engagement metrics
• Device type, OS version, app version, and language
• A pseudonymous Firebase Installation ID and/or pseudonymous analytics identifiers (not linked to your real identity by us)
• Technical metadata attached by the app for analysis (for example: platform, app version, build type/flavor, pseudonymous session ID, and network context flags)

Analytics data is not linked by us to your name, email, or account identity. Stemify does not send audio file content for analytics.

You can limit ads personalisation from Android settings and manage ad consent from the in-app privacy controls (where shown). Analytics data handling is governed by each provider's policies and controls.

Firebase Analytics data is governed by the Firebase Privacy Policy. Mixpanel data is governed by the Mixpanel Privacy Policy.

7. Crash and performance diagnostics

Stemify uses Firebase Crashlytics to collect crash reports and Firebase Performance Monitoring to collect app performance diagnostics. This helps identify and address stability and performance issues.

These diagnostics tools may collect:

• Crash stack traces (technical code location of errors)
• Device model, Android version, and app version
• Whether the app was in the foreground or background at crash time
• Approximate timestamps and pseudonymous installation identifiers
• Performance traces and app/network timing metrics

Crash and performance diagnostics do not include your audio file contents or generated stems.

Crashlytics and Firebase Performance data are governed by the Firebase Privacy Policy.

8. Background processing & foreground service

Stem separation is a computationally intensive task that can take 2–10 minutes depending on song length and device hardware. To ensure this process completes reliably — even if you switch to another app or your device tries to reclaim memory — Stemify runs a foreground service during processing.

What this means for you:

• You will see a persistent notification in your status bar while processing is running (required by Android for all foreground services).
• If you press the Home button or switch apps, processing will continue uninterrupted in the background.
• If you swipe the app away from the Recents screen, processing typically continues while the foreground notification is active. On Android 13+, if notification permission is denied, swiping away may stop processing.
• When processing finishes, the notification updates to show "Done!" and the service stops automatically.
• You can cancel processing at any time by tapping Cancel in the app or the Cancel action in the notification.

9. App permissions

10. Third-party services summary

HTDemucs (the AI model used for stem separation) is open-source software by Meta AI. It runs entirely on your device and does not connect to Meta's servers in any way.

11. Children's privacy

Stemify is not directed at children under the age of 13 and does not knowingly collect personal information from children. The app does not have account creation, social features, or any mechanism by which a child could submit personal information to us.

Please note that AdMob/UMP, Firebase services, and Mixpanel may collect limited device and usage information as described above. If you are a parent or guardian and believe your child has used the app, please contact us and we will work with you to address concerns.

12. Your rights & choices

• Manage ad consent: Use the in-app Ad privacy options control (when shown) to review or update ad consent choices.
• Opt out of ad personalisation: Go to Settings → Privacy → Ads on your Android device and enable "Opt out of Ads Personalisation".
• Reset your advertising ID: Settings → Privacy → Ads → Reset advertising ID.
• Delete stem files: All processed stems are stored on your device. You can delete them at any time via your file manager or from within the app.
• Revoke storage permission: Go to Settings → Apps → Stemify → Permissions and revoke audio/storage access at any time. Note this will prevent you from importing songs.
• Uninstall the app: Uninstalling Stemify removes all locally stored data associated with the app, including cached stems and app preferences.
• Push notifications: You can disable app notifications in Android system settings at any time.
• Analytics/diagnostics data: For Firebase or Mixpanel pseudonymous identifiers, contact us and we will assist with provider-side request paths where available.

Data deletion requests

To request deletion of data associated with your app usage, email stemifylabs@gmail.com with the subject "Data Deletion Request".

Please include your app package name (com.stemify.app) and any device details you can provide so we can locate relevant pseudonymous identifiers.

We can assist with provider-side deletion request paths for pseudonymous identifiers used by Firebase and Mixpanel where those providers support deletion workflows.

Audio files and generated stem files are stored locally on your device and can be deleted by you at any time from the app or your file manager.

We aim to respond within 48 hours. Provider-side completion timelines may vary.

13. Changes to this policy

We may update this Privacy Policy when we add features, integrate services, or respond to legal requirements. When we make material changes, we will update the "Last updated" date at the top of this page.

We encourage you to review this policy periodically. For significant changes, we may show an in-app notice when appropriate.