comparisons

Published by Floriva · Updated 2026-04-29 · How Floriva checks its guides

Natural Cycles vs Stardust: Data Practices Compared

Natural Cycles is a GDPR-covered Swedish medical device. Stardust is a US app that updated its privacy practices after 2022 scrutiny. Here's what each does with your data and when each is the better choice.

Natural Cycles operates under Swedish law and GDPR as an FDA-cleared medical device. Its regulatory framework constrains data practices more than US-based apps face. Stardust is a US app that had documented advertising SDK issues in 2022 and updated its practices afterward. For users choosing between these two: Natural Cycles has stronger structural protections. Stardust has stronger consumer features and US jurisdiction with improved (but not verified-at-architecture-level) practices.

Natural Cycles and Stardust approached each other on the competitive map post-Dobbs, both positioned as alternatives to surveillance-heavy mainstream apps. Their actual data practices are quite different.

Natural Cycles: Regulated Medical Device Data Practices

Natural Cycles occupies an unusual position: it is an FDA-cleared medical device (Class II, contraceptive) and an EU-incorporated company subject to GDPR. This dual regulatory status means its data practices are constrained by both:

FDA medical device requirements: As a cleared contraceptive device, Natural Cycles must maintain specific records, cannot make unsupported efficacy claims, and is subject to FDA post-market surveillance. This does not directly govern data privacy but creates accountability around product claims.

GDPR (Sweden/EU): Health data processed by Natural Cycles is special category data requiring explicit consent. Users have access, correction, and deletion rights. Data transfers to non-EU countries (including the US) require adequate protections. Data can only be used for the purposes users consented to.

What Natural Cycles has stated:

• Does not sell user data

• Does not use health data for advertising

• Processes data to provide the contraceptive service and for product improvement

• Has faced regulatory attention from Swedish Data Protection Authority for specific data practices (analytics data sharing with Facebook for advertising, found to require GDPR consent mechanism updates)

The Swedish DPA finding (2019) is instructive: even a GDPR-covered company can have practices that require correction. The outcome was an updated consent mechanism, not a fine. This is how GDPR enforcement typically works for first-time issues.

Current assessment: Natural Cycles has structural protections from GDPR and medical device regulation that constrain its data practices more than US-based apps face. Not perfect; better than most.

Stardust: Post-Scrutiny US App

Stardust's story after June 2022 is the clearest documented example of what privacy scrutiny produces in the US app market:

1. Dobbs → privacy concerns → users seek alternatives → Stardust surges in downloads

2. Press and researchers analyze the app → find advertising attribution SDK (AppsFlyer) → publish findings

3. User backlash → CEO responds publicly → app updates → SDK removed

4. Stardust updates privacy policy, adds encryption at rest, revises terms

The process worked. Stardust's current version is better than its pre-scrutiny version. The limitation: this process is reactive and depends on continued attention. Without ongoing scrutiny, changes could reverse.

Current Stardust assessment (verify independently):

• Verify SDK presence via Exodus Privacy for current APK version

• Privacy policy now more explicitly limits law enforcement cooperation

• Still US-incorporated, still cloud-based, still requires phone number for registration

Direct Comparison

When Natural Cycles Is the Right Choice

• You want FDA-cleared contraceptive use

• You prefer algorithmic green/red day determination over learning FAM rules yourself

• Stronger structural data protection matters to you

• You're comfortable with a subscription cost for a contraceptive service

When Stardust Is the Right Choice

• Community and social features matter to you

• You prefer a freemium model

• You want a US-based company with improved (if not structurally strongest) privacy practices

• You're using the app primarily for cycle awareness, not contraception

Neither Is Right For

Users who want less readable server-side data. Both Natural Cycles and Stardust store data on company servers and can respond to legal process. For architecture-level privacy, a local-first app is the only option.

What This Means for Floriva Users

The Natural Cycles vs. Stardust comparison shows a spectrum: regulatory structure (Natural Cycles), responsive improvement (Stardust), architectural elimination (Floriva). The strongest data protection is not better compliance. It is not having the data at all.