Privacy Policy

SwingShadow ("the app") is a tennis swing analysis app by Matthew Lee ("we", "us"). This policy covers the Android version distributed through Google Play: what the app does with data, and the choices you have. Write to matthewlee0725@gmail.com with any questions.

Data processed on your device

The app asks the Android system for read-only access to each video you import. It does not copy, modify, move, or delete your video files; they stay where they are in your gallery or storage.

From the video, the app computes and stores the following in its private storage on your device:

• Body pose keypoints (skeletal joint positions detected in each frame).
• Detected swings (forehand, backhand, serve), their timing, and any corrections you make.
• Similarity scores comparing your swings to reference professional templates.
• Court-calibration and analysis metadata.

This data stays on your device unless you share a clip (next section). Delete a video inside the app and the app deletes its analysis; uninstall the app or clear its data and Android removes all of it.

Optional sharing of swing clips

Correct a misdetected swing and the app offers a checkbox: "Upload a video clip of this swing to help improve detection." The app uploads nothing unless you tick that box, and the tick covers that one swing only.

Tick it, and the app uploads the following over an encrypted (HTTPS) connection:

• A short video clip of that swing, a few seconds around the stroke. The app strips the audio track before upload; no sound leaves your device.
• The correction itself: the label the app assigned and the label you corrected it to.
• Technical metadata: app version, detection-model version, video frame rate, clip timing offsets, the model's confidence for that swing, your device model, and the upload time.
• The pose keypoints computed for that clip (numeric joint coordinates, no imagery).
• A random install identifier: a 128-bit number the app draws at random the first time it needs one. It comes from no part of your identity, Google account, or hardware. It groups uploads from the same installation and lets you delete them.

A shared clip is ordinary video: it may show you, and it may show other people on court. Share only clips you are comfortable sharing and have the right to share.

What shared clips are used for

We use shared clips for one purpose: improving SwingShadow's swing detection. We review them and use them as training and evaluation data for the detection models. We do not use them for advertising or profiling, do not publish them, and do not sell or pass them to anyone for their own use.

Where shared clips are stored

The app uploads to our API at api.swingshadow.app. Cloudflare, Inc. (Workers and R2 storage) hosts the data and processes it only on our behalf. Cloudflare operates a global network, so your uploads may pass through data centers outside your country. No one can read a stored clip from the internet: the storage has no public read access, and the endpoints accept uploads only with an access token held by the app.

We keep standard server logs (request metadata, including the install identifier) for a limited period, for debugging and abuse prevention.

Retention and deletion

• Automatic deletion: the server deletes each shared clip and its metadata within 180 days of upload.
• Delete on demand: in the app, open Settings → Privacy → Delete shared clips; the server deletes everything uploaded from your installation on the spot.
• Uninstall the app without doing this and the identifier needed for that request goes with it; the remaining clips still expire under the 180-day rule.

Uploads carry no identity, so we cannot match a clip to an email request. The in-app control is the way to delete your data, and it needs no proof of identity: only your installation holds its identifier.

App permissions

• Internet: carries the clips you chose to share and your deletion requests.
• Notifications: show the progress of video analysis. Optional; analysis runs either way.
• Foreground service and wake lock: keep analysis running while the screen is off.
• Vibration: haptic feedback in the interface.

The app requests no access to your camera, microphone, location, or contacts, and reads no files beyond the videos you pick.

Children

SwingShadow is not directed at children under 13, and we do not knowingly collect personal information from children. The app collects nothing without a share action, stores shares without identity, and builds no profile of any user, child or adult.

Changes to this policy

If we change this policy, we will post the new version at this address with a new effective date. For changes that affect what the app shares or how long we keep it, we will update the app's consent text before the change applies to new uploads.