Privacy Policy
Effective Date: February 14, 2026
String Tension AI ("we," "our," or "us") provides an iOS application that measures tennis string tension using acoustic analysis via your iPhone's microphone. We are committed to protecting your privacy and being transparent about how your data is handled. This Privacy Policy explains what information we collect, how we use it, and your choices regarding your data.
1. Information We Collect
Microphone Audio
Our app requests access to your iPhone's microphone to capture the sound produced when you tap or pluck a tennis string. Audio captured by the microphone is processed entirely on your device and is never transmitted to our servers or any third party. Audio data is analyzed in real time to determine string tension and is immediately discarded after processing — no raw audio recordings are stored.
Measurement Data
When you perform a tension measurement, the app creates a record that may include:
- Calculated tension value (in lbs)
- Frequency analysis results and confidence score
- Timestamp of the measurement
- Associated racquet and string setup profiles you have created
Racquet and String Profiles
You may choose to create profiles for your racquets and string setups. This includes information you voluntarily provide, such as racquet model, string type, gauge, and reference tension.
iCloud Sync Data
If you have iCloud enabled, your measurement data, racquet profiles, and string setups may be synced across your devices using Apple's CloudKit framework. This data is stored in your personal iCloud account and is governed by Apple's Privacy Policy.
Purchase Information
If you purchase a Pro upgrade or other in-app purchases, all payment processing is handled entirely by Apple through the App Store. We do not receive, process, or store any payment card details or billing information.
Information We Do Not Collect
We do not collect your name, email address, phone number, location data, contacts, photos, browsing history, or any other personal information beyond what is described above. We do not use advertising SDKs or third-party tracking tools.
2. How We Use Your Information
The data described above is used exclusively to:
- Perform real-time acoustic analysis and calculate string tension
- Store and display your measurement history and trends
- Generate AI-powered restring recommendations based on your data
- Sync your data across your Apple devices via iCloud
- Enable data export in CSV and PDF formats
We do not use your data for advertising, user profiling, data brokering, or any purpose unrelated to the core functionality of the app.
3. Data Storage and Security
On-Device Storage
All measurement data and user-created profiles are stored locally on your device. The app uses standard iOS data storage mechanisms that benefit from the device-level encryption provided by your iPhone.
iCloud Storage
When iCloud sync is enabled, your data is stored in Apple's CloudKit infrastructure, which encrypts data both in transit and at rest. We do not operate our own cloud servers or databases.
Audio Data
Microphone audio is processed in real time within the app's memory and is never written to disk, transmitted over the network, or stored in any persistent form. Once a tension reading is calculated, the underlying audio data is immediately released from memory.
4. Data Sharing and Third Parties
We do not sell, rent, or share your personal data with third parties.
The only third-party services that interact with your data are:
- Apple iCloud (CloudKit) — for syncing your data across your devices, governed by Apple's privacy policy
- Apple App Store — for processing in-app purchases, governed by Apple's privacy policy
- Apple Crash Reporting — if you have opted into sharing diagnostics with app developers in your iOS settings, we may receive anonymized crash reports to improve app stability
We do not integrate advertising networks, analytics SDKs, or social media tracking tools.
5. Your Rights and Choices
Microphone Access
You can revoke microphone permission at any time through your iPhone's Settings app (Settings > Privacy & Security > Microphone). Without microphone access, the app cannot perform new tension measurements but will continue to display your existing data.
Data Export
The app allows you to export your measurement data in CSV and PDF formats, giving you full portability of your information.
Data Deletion
You can delete individual measurements, racquet profiles, or string setups within the app. To delete all data, you may uninstall the app, which removes all locally stored data. To remove iCloud-synced data, you can manage your iCloud storage through iOS Settings.
For Users in the European Economic Area (GDPR)
If you are located in the EEA, you have the right to access, rectify, erase, restrict processing of, and port your personal data. Since all data is stored on your device or in your personal iCloud account, you have direct control over your data at all times. For any GDPR-related requests, contact us at the email below.
For Users in California (CCPA)
California residents have the right to know what personal information is collected, request deletion, and opt out of the sale of personal information. We do not sell personal information. For any CCPA-related requests, contact us at the email below.
6. Children's Privacy
String Tension AI is not directed at children under the age of 13. We do not knowingly collect personal information from children under 13. If you believe a child under 13 has provided us with personal information, please contact us and we will take steps to remove such information.
7. Changes to This Policy
We may update this Privacy Policy from time to time. When we make changes, we will update the "Effective Date" at the top of this page. For significant changes, we may also provide notice within the app. We encourage you to review this policy periodically.
8. Contact Us
If you have any questions or concerns about this Privacy Policy or our data practices, please contact us at: