Do health apps upload your data? How to check any app, and what Daylumen sends
Some do and some do not, and the answer is in the app's privacy policy and the App Privacy section of its App Store page, not in its marketing. For Daylumen, health data and photos are analysed on the iPhone and never uploaded; what does leave the device is limited to anonymous usage statistics (on by default, can be switched off), an optional weather lookup and an optional membership campaign.
You cannot tell from an app's icon or its marketing. You can tell from two documents and one iOS screen.
Sources: Daylumen's privacy policy (last updated October 11, 2026) and Apple's privacy labels page (apple.com/privacy/labels), checked 2026-10-14.
Check any health app in three minutes
- Open its App Store page and find App Privacy. Apple describes privacy labels as listing the kinds of data an app collects and whether that data is linked to you.
- Read the privacy policy for the words upload, servers, third parties and analytics. A policy that says nothing about where processing happens is itself an answer.
- Check what it can read. In iOS Settings, open Health, then Data Access and Devices, and see which apps can read your Health data. You can switch categories off there.
- Notice whether it needs an account. An account usually means your data lives on a server. No account does not prove nothing is sent, but it removes the most common reason to send it.
A privacy policy is the developer's own statement. The App Privacy label is a second statement to compare it with. If the two disagree, trust neither until you have asked.
What leaves your phone when you use Daylumen
| Item | Sent? | To whom | Can you stop it? |
|---|---|---|---|
| Apple Health data | No | Computed on the iPhone | Not applicable |
| Photos and what is read from them | No | Computed on the iPhone | Not applicable |
| Anonymous usage statistics: a random device identifier, names of in-app events, device and OS info, an approximate region, crash diagnostics | Yes, on by default | PostHog, stored in the United States and relayed through e.daylumen.com | Yes: Settings, Share & feedback, Anonymous usage analytics |
| Weather lookup (optional): approximate location at about city level | Only if you allow location | Apple WeatherKit. Not uploaded to Daylumen's servers | Yes: do not allow location |
| Share & Get Membership campaign (optional): the post link you share, an optional email, install identifier, app version, language and App Store region | Only if you take part | Daylumen's server, and Customer.io if you enter an email | Yes: do not take part |
What the statistics never include
According to the privacy policy, the usage events never include your health data, photos, journal entries or anything else you type or that Daylumen reads from your device. Crash diagnostics carry the crash type, device model and versions, and also never include them.
Where results are kept
Daylumen needs no account. The results of its analysis are cached on your own device so the app opens quickly, and deleting the app removes them.
Frequently asked questions
Does Daylumen upload my Apple Health data?
No. According to its privacy policy, Daylumen reads Apple Health with your permission, only reads and never writes, and does all analysis on your iPhone.
Can I stop everything from leaving my phone?
According to the policy, what leaves the device is the usage statistics, the weather lookup and the membership campaign. Turn off analytics, do not allow location and skip the campaign.
Does Daylumen need an account?
No. The only place an email can be entered is the optional Share & Get Membership campaign.
Does Daylumen sell my data?
No. The privacy policy says health data is never sold or shared with data brokers or third parties, and there is no advertising or cross-app tracking.
Daylumen reads the health data already on your iPhone and tells you what it means for today.
Get Daylumen on the App StoreFree to download · iPhone · iOS 17 or later · a one-time in-app purchase unlocks the deeper tools