Duo Light Privacy Policy

Effective 28 October 2026

Duo Light is a reading lamp for your iPhone. This policy explains what information the app uses, what it sends, and why. In short: there are no accounts and no ads, we don't track you across other apps or websites, and the only data that leaves your phone is anonymous usage information.

What stays on your phone

Your chosen light, brightness and settings are saved on your phone so the app remembers them. They are not sent anywhere except as described below.

Anonymous usage data

To understand how Duo Light is used and make it better, the app sends a small number of anonymous events to PostHog, our analytics provider. These events are:

• When the light turns on or off, how it was turned on or off (opening or closing the phone, the switch, opening or leaving the app, or the auto-off timer), and how long it was on.
• Which light was used (a preset or a custom colour temperature), the brightness, and the auto-off setting.
• When you pick a light preset, change a setting, or finish the welcome screen.
• Whether the app is running on an iPhone Duo or another iPhone.

Along with these events, PostHog automatically receives basic technical information: your device model and manufacturer, iOS version, app version, language and time zone, screen size, and whether you are on Wi-Fi or mobile data. Like any internet connection, the request reaches PostHog from your IP address, but the app tells PostHog not to use it to work out your location.

Each installation gets a random identifier so that events from the same phone can be grouped. It is not linked to your name, email, Apple ID or any account, and it is not your device's advertising identifier.

What we don't collect

• No name, email, phone number or contact details.
• No location, photos, camera, microphone or contacts.
• No advertising identifier, and no tracking across other companies' apps or websites.
• No screen recordings, and nothing you see or do outside the events listed above.

How the data is used and shared

We use usage data only to understand how the app is used and to improve it. We don't sell it, and we don't share it with anyone except PostHog, which processes it on our behalf. PostHog stores the data in the United States. You can read PostHog's privacy policy.

How long we keep it

We keep usage data only for as long as it is useful for improving the app.

Your choices

Because the data is anonymous, we can't tell which events came from you, so we can't look up or delete them individually. Deleting Duo Light from your phone removes your saved settings and its random identifier; if you reinstall, you start fresh with a new identifier.

Children

Duo Light is not directed at children under 13, and we don't knowingly collect personal information from children.

Changes

If this policy changes, we'll update this page and the date at the top.

Contact

Questions about privacy? Email info@serserinc.com.

Duo Light is made by Serser Software Inc.