Clue is one of the safer period tracking apps available, largely because it’s a European company bound by strict EU privacy laws. Your health data is stored on servers in the European Union, not the United States, and Clue states it cannot be subpoenaed by US authorities. The app does not sell your health data to advertisers. That said, “safe” covers several dimensions, from privacy protections to data sharing with researchers, so here’s what you should know before trusting the app with your information.
Why Being EU-Based Matters for Your Privacy
Clue is headquartered in Berlin, Germany, which places it under the General Data Protection Regulation (GDPR), widely considered the world’s strictest data privacy framework. Under GDPR, health data receives special protections that go beyond what US privacy law requires. All user health data is stored on servers located in the EU, regardless of where you live.
This became a major concern after the US Supreme Court overturned Roe v. Wade in 2022, when many people worried that period tracking data could be used as evidence in abortion-related investigations. Clue addressed this directly: because the company is not based in the US, no US court or authority can subpoena user data from Clue. The company is subject to German and European courts, which apply European privacy law and German human rights principles. Clue also pledged publicly that it would notify users and the public if any authority attempted to access their data.
What Clue Does With Your Health Data
Clue’s privacy policy states that the sensitive health data you track in the app is never shared with or sold to advertisers. The company generates revenue primarily through its paid subscription, Clue Plus, rather than by monetizing user data.
There is one notable exception: research. Clue shares de-identified health data with academic research partners to support studies on menstrual and reproductive health. De-identification means your name, email address, and other personal identifiers are stripped from the dataset and replaced with a random ID, so researchers cannot trace the data back to you. One example is a partnership with the University of Exeter’s 4M consortium, which studies connections between menstrual health and mental health conditions.
Clue does share a small amount of technical data with advertising networks, but this is limited to things like preventing you from seeing a Clue ad after you’ve already downloaded the app. The app also shares basic activity signals with certain partners (such as whether you’ve used the app recently), but these signals do not include any tracked health data or anything that would reveal information about your health.
Tracking and Cookies Within the App
While Clue keeps your menstrual data away from advertisers, it does use cookies, third-party services, and a unique identifier tied to your date of birth for analytics, app improvement, and advertising personalization. Mozilla’s Privacy Not Included review flagged this, noting that by using the app, you consent to this tracking by default. If you’re uncomfortable with any data being shared for ad optimization, Clue allows you to change your preferences in the app’s settings.
This is worth understanding clearly: the health data you log (period dates, symptoms, moods) stays protected, but your general app usage patterns and some demographic information like your age are used more broadly. This is a common practice among free apps, but it’s a distinction that matters if you want maximum privacy.
Deleting Your Data
If you decide to stop using Clue, you can request full deletion of your account and data. According to Clue’s support documentation, once you request deletion, your data is irreversibly removed. There is no lingering retention period where your information sits on their servers. However, this also means there’s no way to recover your data afterward unless you made a backup before requesting deletion.
Clue as a Birth Control Tool
Clue offers a separate feature called Clue Birth Control, which is FDA-cleared as a Class II medical device. This means it went through a formal review process and received clearance (under submission K193330) as a software application for contraception. It uses your period start dates to predict high-risk and low-risk days for pregnancy based on fertility awareness methods.
This feature is designed for people aged 18 to 45 with predictable cycles between 20 and 40 days who haven’t recently used hormonal birth control. Fertility awareness methods are less effective than hormonal contraception or IUDs, so whether this feature is “safe” depends on your tolerance for pregnancy risk. The FDA clearance means the algorithm meets regulatory standards, but no fertility awareness method is as reliable as other contraceptive options.
How Clue Compares on Privacy
Among period tracking apps, Clue consistently ranks well in independent privacy reviews. Its EU jurisdiction, GDPR compliance, and clear public commitments around law enforcement requests set it apart from US-based competitors that fall under less protective data laws. The Mozilla Foundation’s review confirmed that Clue does not sell user information, though it noted the limited data sharing for advertising and research purposes described above.
No app offers perfect privacy. Clue collects data because it needs your cycle information to function, and it uses some technical data for business purposes. But compared to many alternatives, it provides stronger legal protections, clearer policies, and more transparent communication about what happens with your data. If privacy is your primary concern when choosing a period tracker, Clue is a reasonable choice, particularly if you take the extra step of adjusting your ad-related data sharing preferences in the app’s settings.