After the Supreme Court's Dobbs v. Jackson decision in 2022, millions of people started asking a fair question about their period tracker: where does this data actually go? Cycle data is some of the most intimate information you can put in an app. If you're searching for a private period tracker, this page lays out Crimson's approach in plain terms, plus the questions worth asking any app.
Why period tracker privacy is different
Most health apps in the US aren't covered by HIPAA, the law people assume protects their medical data. That gap has real consequences. In 2021, the FTC settled with Flo, the most downloaded period tracker in the world, after alleging it shared users' health data with third parties including Facebook and Google despite promising it wouldn't. Flo has since updated its practices, but the episode made one thing clear: privacy promises are only as good as the architecture behind them.
So when you evaluate a private period tracker, look past the marketing. Ask what leaves your device, who can read it on the server side, and how fast you can make it disappear. You can see how the major apps stack up in our period app comparison.
How Crimson stores and protects your data
Local-first storage. Your health data lives on your device first, using local storage. Cloud sync keeps a copy backed up and available across your devices, scoped to your account in our Convex-hosted database so only you can access your records.
Encryption. Data travels over HTTPS with TLS 1.2 or newer and is encrypted at rest. We won't claim end-to-end encryption, because Crimson doesn't have it, and you deserve the accurate version over the impressive-sounding one.
Never sold. We don't sell your data to third parties, don't share health data with advertisers, and don't build advertising profiles from your cycle history. That's not a settings toggle. It's just how the business works.
What Crimson collects, and why
- Health data you enter: period dates, cycle lengths, symptoms, moods, daily logs, and fertility information. Used only to show your history, calculate predictions, and generate insights.
- Your email address: collected at sign-in and managed by Clerk, our authentication provider. That's the whole account record.
- AI chat messages: if you use the AI assistant, your messages are processed to generate answers. More on that below.
Nothing else. The full legal version lives in our privacy policy.
The AI assistant and your data
Crimson's AI works out of the box, and it only touches your health data with your explicit consent. When you opt in, requests include your chat messages plus a limited context: your current cycle phase and day, symptoms and moods from your last 7 logged days, and your pregnancy week or hot-flash details if those modes apply. Your name, email, and account identifiers are never included. One honest caveat: zero-cost AI models may retain prompts, so non-retention can't be guaranteed on the provider side. Revoke AI data sharing anytime in Settings and no health data goes to any AI service.
Why Crimson requires an account
An account is required, and it's there for your benefit. Sign-in through Clerk keeps your synced records behind authentication instead of tying them to a device anyone can pick up. It's also what makes cross-device sync, data recovery, and server-side AI usage limits possible. The account holds your email address, not your identity papers.
Your rights, in plain terms
You can access everything we store about you, and you can take it with you. CSV export with date filtering and PDF cycle or pregnancy reports are built into the app and completely free, no subscription needed. If you want out, the delete-account option in Settings removes your account and all associated cloud data. Questions go to support@getcrimson.app.
New to cycle tracking? Our cycle guide covers the basics, phases, and what your symptoms are telling you.
Frequently asked questions
Do period tracker apps sell your data?
Some have shared data in the past. In 2021 the FTC settled with Flo after alleging it shared users' health data with third parties including Facebook and Google, despite promising otherwise. The safest check is the app's own privacy policy: look for plain language about selling data and third-party sharing. Crimson's policy is short on purpose. We never sell your data, never share health data with advertisers, and never build ad profiles from it.
Can period tracking data be subpoenaed?
This isn't legal advice, and laws vary by state and country. In general, data held by any company can be subject to legal process, and most period trackers aren't covered by HIPAA. Data stored only on your own device is harder for third parties to reach than data sitting on a server, but no setup makes data impossible to obtain. If legal exposure is a concern for you, keep less data in the cloud, know how to delete it quickly, and talk to a lawyer about your specific situation. Crimson lets you delete your account and all synced data at any time from the app's settings.
Does Crimson require an account?
Yes. Crimson uses Clerk for secure sign-in, and your account is what keeps your synced records scoped to you and only you. It also enables cloud backup across devices and lets us enforce fair AI usage limits server-side. We collect only your email address for sign-in, handled by Clerk; your health data is never used for advertising.
How do I export or delete my Crimson data?
Both are built in and free. You can export your history as a CSV file with date filtering, or generate PDF cycle and pregnancy reports to share with a doctor. To delete everything, use the delete-account option in the app's settings: it removes your account and all associated cloud data. Questions go to support@getcrimson.app.
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