Reproductive health data is unusually sensitive. It can indicate whether someone is pregnant, trying to conceive, dealing with hormonal conditions, or at stages of life they may not have chosen to share publicly. As the political and legal landscape around reproductive rights has shifted in many parts of the world, the question of who holds this data — and what they can legally do with it — has never carried more weight.
Most period tracking apps are free because they monetise their users' data. The information people log in these apps — cycle phases, fertile windows, pregnancy test results, symptoms, and more — is exactly the kind of intimate health data that advertisers, data brokers, and in some jurisdictions, third parties you'd never choose to involve, may be able to access. Before you hand that data over, it's worth knowing what you're agreeing to. This guide covers what to look for in a privacy-first tracker, how Mozi handles your data, and the warning signs that an app isn't treating your privacy seriously.
What to look for in a private period tracker
- It does not sell or share your health data with advertisers or third parties. This should be explicit in the privacy policy — not hidden in vague language. Apps that monetise through advertising often share user data with ad networks, which can include sensitive health information you logged in good faith.
- It offers a guest or offline mode. If an app requires you to create an account before you can use any features, your data is tied to an identity from the very first entry. A guest mode means you can track locally without creating an account — meaning your data never leaves your device unless you choose it to.
- All data is encrypted in transit and at rest. Encryption protects your data from being read even if it is intercepted during transmission or exposed in a breach. This should be a baseline requirement, not a premium feature.
- The app makes it easy to delete all your data. A privacy-respecting app should let you permanently delete your account and all associated data with a few taps — not bury the option in a support ticket process. Transparency about what happens to your data after deletion matters too.
- It complies with GDPR and CCPA. These are the most comprehensive data protection frameworks currently in effect. GDPR compliance means the app must get meaningful consent, allow access to your data, and enable deletion. CCPA gives users in California the right to know what data is collected and to opt out of its sale. Compliance with both is a meaningful privacy signal.
- The app does not serve ads or use your data to build advertising profiles. Ad-supported apps almost always collect behavioural and demographic data to target you. In a period tracking app, that means your health data is being processed and categorised for advertising purposes — which is a fundamentally different relationship with your data than a subscription model.
How Mozi approaches your data
Mozi was built around a core principle: your reproductive health data belongs to you, and no one else should profit from it. Mozi does not sell your health data, does not share it with advertisers or data brokers, and does not use it to build advertising profiles. That's not a marketing claim — it's how the app is engineered.
One of the most important features for privacy is guest mode. Mozi lets you start tracking immediately — no email address, no account, no identity required. If you choose to create a free account later to sync across devices, your existing guest data transfers over. All data is encrypted in transit and at rest. Mozi is GDPR and CCPA compliant, which means you have the right to access, export, and permanently delete all of your data at any time — and the delete function is built directly into the app, not hidden behind a support form.
Mozi is also entirely free of advertising. There are no ad networks, no third-party tracking SDKs, and no background data sharing with partners. The premium subscription is what funds the product — not your data. Read the full Mozi privacy policy for complete details on what is and isn't collected.
Red flags to watch for in any period app
- The app requires an account before you can use any features. This means your data is tied to an identity from the very first entry. Even if the app says it doesn't share data, creating an account means your information exists on their infrastructure with a direct link to you from day one.
- The privacy policy uses vague language about sharing data with "partners" or "affiliates". This is one of the most common ways apps obscure data sharing. "Partners" and "affiliates" can include advertising networks, analytics companies, and data brokers. If the policy isn't specific about who receives your data and why, assume the scope is broader than you'd want.
- There is no clear data deletion option in the app settings. If you can't find a "Delete my account and all data" button within the app itself, that's a significant warning sign. Apps that make deletion difficult are often designed to retain data — and revenue — even after users leave.
- The app is free but serves ads. Advertising-supported apps nearly always collect behavioural and demographic data to serve targeted ads. In a period tracking app, that means your health data is being processed and categorised to show you relevant advertising — which is a fundamentally different relationship than a subscription model.
- The app has a history of data breaches or selling user data to third parties. A quick search of any app's name alongside "data" or "privacy" will often surface past incidents. This history matters — a company that has monetised user data once, or failed to protect it, has demonstrated where its priorities lie.