Privacy Review: Stardust Period Tracker

Stardust’s default setup raises some clear privacy concerns. From the moment you open it, the app sends data to third-party tracking services, even before you’ve had a chance to enter any information.

As you use the app, it sends more detailed information, including your birthdate, birth control type, reproductive goals, and even specific symptoms, to third-party services. Some of this data is sent to a mix of third-party services, including analytics tools, attribution services, and data pipelines that can pass it along to other companies.

We couldn’t find clear in-app settings to fully disable this data collection or transmission. While iOS does offer some system-level controls to limit tracking, the app itself doesn’t provide much control over what gets shared once you start using it.

Stardust lets you track just about every facet of your reproductive health. For starters, this includes your moods, cravings, cramps, headaches, appetite, energy levels, alcohol consumption, and whether or not you’re pregnant or using a certain kind of birth control.

The app also tracks how you use it: whether reminders are on, whether Apple Health sync is enabled, and whether you’re a paid user.

An analysis from Privacy International found that Stardust shares user data with a range of third-party analytics providers, including personal details like users’ first and last names. Around the same time, Gizmodo reported that Stardust was promoting itself as an “encrypted” and privacy-safe alternative in the wake of Roe v. Wade, even as critics questioned what those claims actually meant in practice. Later reporting from TechCrunch found that what Stardust was actually offering was standard SSL and server-side encryption, not the end-to-end encryption it had promised. Stardust scrubbed end-to-end encryption claims from its privacy policy following the report.

Meanwhile, Stardust's privacy policy keeps getting longer. According to snapshots tracked by Berkman Klein, it was revised twice in roughly seven months, each time disclosing more about the device and advertising data it collects—including, as of May 2026, naming Meta's and Google's ad-measurement tools as partners it shares activity data with. Its separate Health Data Privacy Policy has stayed put since October 2025, still making the same core claim: health data sits under a randomized ID, walled off from your name or contact info.

Finally, one recent academic analysis from the University of Illinois found no evidence of Stardust sharing health data with advertisers through its Android app—consistent with what we found in our own testing.

We didn’t find evidence that Stardust sells user data in the traditional sense, like directly passing it to data brokers for resale, but that doesn’t mean data isn’t being shared.

We only found one partner transmitting detailed health data directly: RudderStack, a platform that apps use to collect and route user analytics. The moment we logged a symptom, RudderStack received the details, what it was, and when, alongside a persistent user ID.

The company said it uses RudderStack as an intermediary pipe to carry data into its analytics system. “Stardust does not provide RudderStack with any information that can identify the user,” said a company spokesperson.

Stardust also shared basic device and usage data with two marketing partners, AppsFlyer and Facebook, including, in Facebook's case, an ad identifier tied to our device. By design, it lets Facebook tie a user's behavior inside Stardust to whatever data it already has on them.

Most of the data collection we saw was happening through analytics and tracking systems, rather than through direct access to things like your location, contacts, or other sensitive device data, which makes it less invasive than apps that rely on broad device permissions.

It also doesn’t lean heavily on traditional advertising to monetize, which can limit some of the more aggressive tracking that often comes with ad-driven apps.

Like most apps, Stardust sends data to third-party services, including partners for analytics, tracking, and data routing. Not all of that data is innocuous; in some cases, the data being shared can include things like your birth control method, like whether you use medication or an IUD, your reproductive goals, like whether or not you’re trying to conceive, and even specific symptoms you log, like whether you have tender breasts, headaches, or stomach cramps.

One of the tools in this mix, RudderStack, is built to route data to destinations we couldn’t observe during testing. Stardust told us RudderStack is only routing your information to their analytics system, but your data may be reaching more companies than the ones we named here. We couldn’t find an obvious way to fully disable third-party analytics within the app.

Stardust says users can contact the company to have their data deleted.

Outside the app, iOS settings like App Tracking Transparency, the pop-up asking if you permit apps to track you, aren’t designed to target these kinds of data sharing setups.

These steps won’t stop all of Stardust’s data sharing, but they can help reduce how much of your information is collected and where it ends up.

• Watch what you log. Because the app can share detailed information about what you log, like birth control choices and symptoms, with third-party services, it may be worth thinking twice before entering that kind of information unless you really need to.
  
• Turn off Apple Health sync or other integrations. Turning this off means less data gets shared between the app and other services, both in and out.
  
• Skip the social features. Inviting or connecting with friends adds another data point that gets tracked and shared, including when you invite or connect with other users.
  
• Log out when you’re done. Session data is collected while the app is active; closing it limits how long that window stays open.

Stardust’s privacy issues aren’t entirely unique. Just about every app you’ll use relies on behind-the-scenes tracking that happens out of view. But that context only goes so far when you’re talking about an app designed to keep tabs on your reproductive health. In our testing, using the app was usually enough to share those details with outside companies, not as an edge case, but by default.

Stardust markets itself as a safe space for sensitive health data. That framing matters: an app that promises discretion is often one that ends up knowing more. None of this is to say you need to stop using Stardust if you do. It just means not taking a company's privacy claims at face value.