A private migraine diary

Why headache data is sensitive

A migraine diary is not a step counter. It records when you were incapacitated, what medication you took, how your episodes track with sleep, stress, or your menstrual cycle. That is exactly the kind of data that has repeatedly ended up where it did not belong.

In January 2021, the FTC settled with Flo Health after alleging that the period-tracking app, used by more than 100 million people, disclosed users' health data to marketing and analytics companies including Facebook's and Google's analytics divisions, after promising to keep it private.[1] In May 2023, the FTC moved to bar the ovulation-tracking app Premom from sharing users' personal health data with third parties for advertising, again after privacy-policy promises to the contrary.[2] And it is not just apps: ProPublica has documented how insurers and data brokers assemble intimate lifestyle profiles, from bill payments to shopping habits, to estimate what your care will cost them.[3]

None of this requires bad intentions on day one. Data that sits on a company's servers is subject to policy changes, acquisitions, breaches, and subpoenas. The only data that can never be mishandled is data that was never collected.

How Cephalo stays private

Cephalo is built so that your diary never has to leave your hands:

• No account. There is no sign-up, no email, no login. Open the app and start logging.
• On-device by architecture. Your entries are stored on your iPhone, and every insight is computed there too. The app works fully offline because there is no server doing the work.
• Your iCloud, not our cloud. If you want backup and sync across devices, optional iCloud sync stores your diary encrypted in your personal Apple account. We never see it.
• A privacy label you can check. Cephalo's App Privacy section on the App Store lists only data not linked to you (purchases, anonymous identifiers, usage statistics) and no health data collection.[4]

What you still get

Private does not mean bare-bones. The free diary includes unlimited episode logging, a medication log with overuse warnings, the MIDAS questionnaire, calendar and history views, and a doctor-ready PDF report of your episodes, medication use, and patterns to bring to your next appointment. Cephalo Plus optionally adds trigger analysis with confidence levels, extended analytics, and automatic weather correlation, all still computed on your device.

Frequently asked questions

Is a migraine diary without an account still backed up?

Yes, if you want it to be. Cephalo offers optional iCloud sync: your diary is stored encrypted in your personal iCloud account and restored on a new iPhone. It is off until you turn it on, and it never involves our servers.

Can my headache data be sold or shared with advertisers?

No. Your entries never leave your device unless you export them yourself or enable iCloud sync into your own Apple account. There are no third-party trackers or ad SDKs in the app, and Cephalo's App Store privacy label lists no health data collection.

What does on-device actually mean?

Your episodes are stored in a database on your iPhone, and the analysis (patterns, trigger analysis, reports) is computed by your iPhone. That is why the whole app works offline: there is no server doing the work.

Can I still share my diary with my doctor?

Yes. You can generate a clear PDF report of episodes, medication use, and patterns whenever you choose, and hand it over yourself. Sharing is always an action you take, never something that happens in the background.