Privacy Policy
Wavelength for iOS. Effective July 29, 2026.
Overview
Wavelength is built by Impulse Arc LLC. The app does not collect, store, or transmit anything that identifies you. It does send us a small number of anonymous events about how the app itself is being used, described under Usage measurement, so we can tell where the app is confusing people. The only personal data we ever collect is an email address you choose to give us on one of our websites, described under Email. This policy explains all three.
Camera access
Wavelength uses your iPhone camera to measure ambient light levels and estimate melanopic lux from the color temperature and exposure parameters reported by the camera hardware. Camera data is processed entirely on your device in real time. No images or video are captured, stored, or transmitted.
The numbers it works out — a light level, a colour temperature, the time — are kept, because the plan for tomorrow depends on the light you got today. They stay on your device and sync across your own devices through your iCloud account, which is how the widget and the Mac app show the same advice as the phone. They are never sent to Impulse Arc LLC.
Sleep schedule data
You may enter your target bedtime and the time you woke up within the app. This information is stored locally on your device and synced across your own devices via iCloud (using CloudKit). It is not accessible to Impulse Arc LLC or any third party.
Apple Health
If you turn on “Read sleep from Apple Health”, Wavelength reads two things: your sleep analysis records, so it can fill in what time you woke up instead of asking you, and the minutes your Apple Watch recorded as time in daylight, so the plan knows the light you actually got. It reads those two categories and nothing else, and it never writes anything back to Health.
Health data is used to work out where your body clock is and when to advise light. What Wavelength derives from it — your wake times, and the stretches your watch called daylight — is stored on your device and syncs across your own devices through your iCloud account, the same way your bedtimes do, so every part of the app answers from the same record. It is never sent to Impulse Arc LLC or to any server we run, never used for advertising or marketing, and never shared with or sold to anyone. Turn the switch off at any time, or revoke access in the Health app, and Wavelength goes back to asking you.
Notifications
If you enable notifications, Wavelength schedules local notifications on your device for light exposure reminders. These are generated and delivered entirely by iOS. No notification data is sent to any server.
If you enter your email address on one of our websites, we store it solely to reply to you and send occasional notes about the app. It is held by our hosting provider, Cloudflare, is never sold or shared, and is not used for advertising. Ask us to delete it at any time by emailing wavelength@impulsearc.com.
Usage measurement
Wavelength includes no analytics frameworks, no advertising SDKs, and no third-party tracking of any kind. No advertising or analytics company receives anything from the app.
The app does report a short list of anonymous events to a server we run ourselves, on our own domain: that the app was installed, that it was opened (and on which day, counted from the install), that a light reading was produced, whether camera access was granted, that the subscription screen was shown, and that a free trial or a subscription started. Each event carries a random identifier generated on your device the first time the app runs, the app version, and, if the install came from an Apple Ads search ad, the campaign and keyword Apple reports for it. That is the whole list.
The random identifier is not your Apple ID, your device ID, or your advertising ID. It is not linked to your name, your email, or any other identifier we hold, it is not shared with anyone, and we cannot use it to work out who you are. Your light readings, your sleep times, any data read from Apple Health, and your location are never sent.
We use these events for one thing: counting how many people who install the app get as far as a reading, a subscription screen, and a trial, so we can find and fix the places people get stuck. Deleting the app deletes the identifier; reinstalling generates a new, unconnected one. We do not collect crash reports.
Data sharing
We do not sell or share your personal information, and we do not use any of it for advertising. The only personal data we may hold is an email address you optionally provide on one of our websites, described under Email. The usage events described above hold no personal data to share.
Children
The Wavelength app does not collect personal information from anyone, including children under 13. The anonymous usage events described above contain no personal information and no age information.
Changes
If this policy changes, the updated version will be posted at this URL with a new effective date.
Contact
Questions about this policy: wavelength@impulsearc.com