Privacy policy

Last updated: 17 October 2026

Who we are

Crownwind is made by Mirentha Ltd, a company registered in England and Wales (company number 17207914), at 71-75 Shelton Street, Covent Garden, London, WC2H 9JQ. You can write to us about privacy at [email protected].

This policy covers the Crownwind app. Visits to mirentha.com, and messages sent with the support form, are covered by our website privacy policy.

What Crownwind keeps on your iPhone

Everything you record is kept in the app’s own storage on your iPhone:

• Your watches: the name, movement, beat rate, target range, whether it’s quartz, the purchase date, the service interval, a photo and notes.
• Your syncs: the true time of the tap, how far the watch was from true time, how far apart your three taps were, whether the phone’s clock was checked (and the check’s offset and round trip), whether the sync started a new run, how the watch spent the interval (worn, dial up and so on) and any note.
• Three readings that spot a changed phone clock: with each sync Crownwind also stores a reading of the phone’s running clock, an identifier for the phone’s current start-up session, and the identifier iOS gives this iPhone for Mirentha’s apps. They’re only compared with each other, to tell whether the phone’s clock was changed or the phone restarted between two syncs. The running-clock reading is shifted by a random amount each time the phone starts, and that amount never leaves the phone, so no record shows when your phone was started.
• Your services: the date, who did it, the cost, the work done and a note.
• Photos: a watch’s photo is chosen with the system’s photo picker, which needs no permission and gives Crownwind only the photo you pick. It’s re-saved as a JPEG of at most 1,600 pixels, which drops its location and other details.
• A few settings, on the phone only: how many rate results you’ve seen and the app version in which it last asked Apple to show its rating prompt, the date of the newest backup, the storage format’s version, your plan and when the App Store last confirmed it, whether quartz watches show seconds a month, and the random shift above.

Mirentha doesn’t process any of this: it stays on your devices and in your own iCloud. Your iPhone’s own backups (to iCloud or a computer) include it, as they do for any app.

iCloud

If you’re signed in to iCloud, Crownwind keeps a copy of your watches, syncs, services and photos in your own private iCloud database, so your other devices signed in to the same Apple Account see the same records. Apple stores it under your Apple Account; Mirentha can’t read it. Apple uses silent notifications to tell the app when there are changes to fetch. If you aren’t signed in, Crownwind works on the iPhone alone. The settings above, the backup files and exports aren’t part of Crownwind’s iCloud copy.

The time check

When the Sync screen opens, and again after your third tap, Crownwind asks Apple’s time server, time.apple.com, how far the iPhone’s clock is out. Each check is three small requests (48 bytes, over the internet’s time protocol, SNTP) a fifth of a second apart. A request carries only the phone’s current time, which the server sends back with its own. Like any request on the internet, it shows your IP address to Apple; it contains nothing about you, your watches or the app, and Mirentha receives nothing from it. Apple’s handling of it is covered by Apple’s privacy policy. With no connection, the sync is still kept, marked “Clock not checked”.

Backups and exports

Each week Crownwind writes a backup file of every watch, sync and service (photos included) to Files › On My iPhone › Crownwind, named by its date, and keeps the newest eight. Before an update changes how the app stores your records, it copies them there first. You can also export a CSV file (one row per interval, for a spreadsheet) or a JSON file (everything, the same format as a backup). These files leave your iPhone only if you move, save or share them somewhere else.

Service reminders

If you set a service interval, Crownwind asks to send notifications, and schedules them on your iPhone: 30 days before a service is due and on the day, at 09:00. Nothing about them is sent to us. You can turn them off at any time in your iPhone’s Settings › Apps › Crownwind › Notifications.

Apple, the only third party

The only third party that receives anything from Crownwind is Apple: your iCloud copy, the time check, notifications and purchases. We confirm that Apple gives this data the same or equal protection as this policy describes, under Apple’s privacy policy. Crownwind shares nothing with anyone else.

Purchases

Crownwind Plus is bought through Apple’s App Store. Apple handles the payment; Mirentha never sees your payment details and receives only Apple’s sales reports, which don’t identify you. The app asks the App Store whether Plus is active and keeps the answer, and when it was last confirmed, on the phone.

Crash reports

Crownwind contains no analytics, crash-reporting or advertising code. If you’ve chosen to share analytics with app developers (Settings › Privacy & Security › Analytics & Improvements), Apple may share crash reports and usage statistics with us; they don’t identify you to us.

Keeping and deleting your records

Your records stay until you delete them. Deleting a watch in Crownwind deletes its syncs and services too, on every device that syncs with your iCloud. Deleting the app removes what’s on that iPhone, but not your iCloud copy or any files you’ve exported; to remove the iCloud copy, go to Settings › [your name] › iCloud › Manage Account Storage. Backup files can be deleted in the Files app. Because Mirentha holds none of your records, there’s nothing for us to delete, but we’re glad to help: write to [email protected].

Your rights

Under UK data protection law you have the right to access, correct, erase, restrict or object to the use of your personal data, and to take it with you. For the app, Crownwind’s own export and delete give you these directly, as we hold nothing from it. If you’re unhappy with how we’ve handled your data, please tell us first; you can also complain to the Information Commissioner’s Office at ico.org.uk.

Children

Crownwind isn’t aimed at children under 13, and we don’t knowingly collect personal data from them.

Changes to this policy

If the app starts handling data differently, we’ll update this page and its date before the version that does so is released.

Contact

Mirentha Ltd, 71-75 Shelton Street, Covent Garden, London, WC2H 9JQ. Email [email protected].

See also the terms of use and support.