Clefle
Privacy
Last updated: September 23, 2026
Clefle has no accounts and collects no personal data. Your progress, settings and microphone calibration stay in the browser on your own device and are never sent anywhere. Sound from your microphone is analysed on the spot; it is never recorded or stored. Clefle does count anonymous usage — such as how many sessions are finished — with no cookies and nothing that identifies you.
Who is responsible
Clefle is made and run by The Clefle team. Contact: [email protected].
What the app stores on your device
The items below live in your browser's own storage (IndexedDB and localStorage) on the device you're using. They don't leave it.
| What is stored | Why |
|---|---|
| Progress on each note: how often you've seen it, how often you got it right, when to review it next | To bring a note back just before you'd forget it |
| A log of your answers: when, which exercise, right or wrong, how long it took, which note you picked by mistake | The progress page, and spotting which notes you mix up |
| Settings: your level, kids' or adults' mode, music-stand mode, language, note names | So the app opens where you left off |
| Two microphone calibration numbers: the background noise level of your room, and your reference pitch for A | To check pitch correctly for your microphone and your room |
| Your light or dark theme choice | To remember it |
Clefle does not use cookies.
The microphone
The microphone is only turned on when you choose the play-along exercises and allow it in your browser. The sound is analysed on your device, a few hundredths of a second at a time, to find its pitch — and then discarded. Clefle does not record, store or send any audio. The only thing kept is the two calibration numbers above.
You can withdraw microphone permission at any time in your browser settings.
Anonymous usage statistics
To learn whether Clefle actually helps people, it counts a few things. These counts go to Umami, a privacy-focused analytics service, and only from clefle.com:
- which page was opened, the page it was reached from, your browser's language and your screen size;
- six events: the app was opened, a session started, a session was finished, a session was left halfway, a level was unlocked, the microphone was calibrated;
- with those events, a few labels: kids' or adults' mode, the level, the app language, the note names you use, whether the app is installed, the rough accuracy of a finished session (0–49%, 50–79% or 80–100%), and the reference pitch from calibration.
Umami also works out your country and your browser and device type from the request, as any web server can. It uses no cookies, stores nothing on your device, and does not store your IP address. Nothing sent can tell who you are, and your answers, your progress and your microphone never leave your device.
If your browser has Do Not Track or Global Privacy Control turned on, Clefle sends nothing at all.
Error reports
If something breaks in the app, Clefle sends the error message, where in the code it happened, and the app version — through the same channel, with the same limits. At most three per visit.
What is never sent
No accounts, no ads, no advertising or social media trackers, no embedded social media buttons. Fonts, violin sounds and code are all loaded from this site; the only other service Clefle talks to is Umami, as described above.
Like any website, the server hosting Clefle may keep standard technical access logs — IP address, browser type, time of request — to run the service and protect it from attacks. Those logs contain nothing about your progress and are not linked to it.
When you send feedback
The "Send feedback" link opens your own email app with a message already started. Nothing is sent until you press send yourself. If you do, we receive what any email contains — your email address and your message — plus the technical details at the bottom of it: the app version, your browser, your screen size and your Clefle settings. You can read and delete any of that before sending.
We use your email only to reply and to fix the problem you reported, and we don't share it with anyone.
Children
Clefle has a kids' mode. Because the app collects no personal information from anyone, it collects none from children either, and none of a child's data leaves the device. We still suggest a parent sits alongside the first time a child turns on the microphone, so they understand what the browser is asking for.
Your control over this data
- See it and take it with you: "Save progress to a file" on the start screen downloads everything the app has stored. "Restore from a file" loads it on another device.
- Delete it: clearing this site's data in your browser settings deletes it completely. We hold no copy, so there's nothing else to delete on our side.
- Keep in mind: because no copy exists anywhere else, clearing browser data or switching devices loses your progress. Save it to a file first.
Because we hold no personal data, requests to access, correct or erase data held by us — under the GDPR, UK GDPR, or US state privacy laws — have nothing to act on. You're welcome to contact us anyway.
When this policy changes
If Clefle ever adds accounts, syncing between devices, or usage statistics, this page will be updated before the change takes effect, with the date and a clear description of what is sent and to whom. Anything that needs your consent will be asked for before it happens.
Contact
Questions about privacy: [email protected].