menstrudel.app

In One Sentence

menstrudel.app is a free, open-source, offline period-tracking app for women worldwide, maintained by an independent developer team in the United States, with a strong focus on privacy-first design and an ad-free experience. It does not rely on cloud servers, and all data is stored locally on the user’s device, so it can be used without registration or an internet connection. This makes it especially suitable for users who are highly sensitive about personal health data and want full control over their menstrual cycle records.

Business Overview

The core service offered by menstrudel.app is period and ovulation prediction. Users can manually record period start/end dates, symptoms, moods, discharge, and other physiological indicators, while the app uses an algorithm to estimate the next period and fertile window. The app has no monetization model of any kind: no ads, no data collection, no in-app purchases. Its code is fully hosted on GitHub for review and further development.

The project originated as a response to privacy concerns around mainstream period-tracking apps, many of which monetize by selling health data. menstrudel.app takes a fully offline, open-source, zero-network-request approach, making it a niche but highly regarded option in the overseas health-tracking space. Its users are mainly technically literate women, privacy advocates, and people who do not want to pay for period tracking. It currently does not offer enterprise services or team collaboration features.

Who It’s For

• Privacy-sensitive users: Women who do not want their period data uploaded to any server. menstrudel.app is one of the few options that can truly keep all data stored locally.
• Tech enthusiasts and developers: Its open-source nature allows users to modify features, contribute code, or integrate it into a personal health management setup.
• Offline-use scenarios: Suitable for travel without internet access, areas with unstable signal, or users who intentionally reduce phone connectivity.
• Users with a zero budget: Completely free, with no paywalls or feature restrictions.
• Not suitable for: Users who need cloud sync, multi-device sharing, pregnancy mode, data sharing with doctors, or who prefer polished graphical UIs and community features.

Key Features and Highlights

• Fully offline operation: No internet connection is required. Data is stored only on the phone locally, with no network requests, fundamentally reducing the risk of data leakage.
• Open source and auditable: All source code is available on GitHub, allowing anyone to check whether hidden data-collection code exists. Users can also compile and install it themselves.
• No ads or tracking: The interface is clean, with no third-party ads or analytics tools. It does not collect device fingerprints or usage behavior.
• Basic prediction algorithm: Based on user-entered cycle length and period duration, it automatically estimates the next period, fertile window, and ovulation day. The algorithm is transparent and adjustable.
• Custom record fields: In addition to standard symptoms, users can add custom tags to support different physiological tracking needs.
• Lightweight and cross-platform: Built with web technologies, it can be packaged as a desktop app or mobile PWA, with very low resource usage.

Pricing Analysis

menstrudel.app is completely free, and all features are available without paying anything. In the period-tracking app market, most comparable products use a subscription model, such as Flo at around $10/month and Clue at around $5/month, or a one-time/annual purchase model, such as Natural Cycles at around $80/year. By contrast, menstrudel.app costs nothing to use.

Because the project depends on the developer’s personal time and donations, there are no hidden fees or paid upgrade options. However, it is worth noting that it also does not provide the advanced features typically reserved for paid tiers, such as cloud backup, medical-grade algorithms, or expert consultation. There is also no refund policy because there is no payment process at all. For budget-conscious users, it is one of the best-value choices; for users looking for commercial-grade service, the missing features should be considered carefully.

How Chinese Users Can Use It

• Network accessibility: It works well from mainland China because the app itself does not depend on any overseas servers. Once downloaded and installed, it can be used completely offline. The initial installer can be obtained from GitHub or third-party mirrors. Some mirror sites may require a VPN/proxy to access, but after installation, no internet connection is needed for daily use.
• Payment methods: No payment is required, so there are no payment barriers.
• Whether a VPN/proxy is needed: A VPN/proxy may be needed to access GitHub when downloading the installer, but it is not needed for everyday use. If the installer is obtained via a domestic app store or cloud drive, the whole process can be completed without bypassing restrictions.
• Domestic alternatives: China has free apps such as “大姨妈” and “美柚”, but they generally require online registration, upload data, and have advertising and privacy controversies. menstrudel.app is one of the few options that can work fully offline, though its interface is in English and it has no Chinese community support.
• Invoice issues: Invoices cannot be issued because the project has no commercial entity and involves no transaction.

Pros and Cons

Pros:

• ✅ Completely free, with no paid traps
• ✅ Extremely strong privacy protection, with 100% local data storage
• ✅ Open source and auditable, with transparent code
• ✅ Works offline and does not depend on the internet
• ✅ No ad interruptions, with a minimalist interface

Cons:

• ❌ English-only interface, with no Chinese localization
• ❌ Basic feature set, lacking advanced functions such as symptom chart analysis, pregnancy mode, and health report export
• ❌ No cloud sync, so data may be lost after changing phones or reinstalling the app
• ❌ No official customer support or community support; issues must be researched through GitHub issues
• ❌ Simple algorithm that may not suit irregular cycles or medical diagnostic needs

Comparison with Similar Products

• Flo: Uses a paid subscription model and offers AI-driven cycle prediction, pregnancy mode, and medical articles, but data is uploaded to the cloud and its privacy policy has previously been questioned. Suitable for users willing to pay and who need rich features.
• Clue: Uses a free + subscription model, has an attractive interface, and supports data export, but some data still involves network connectivity. Its privacy protection is moderate, making it suitable for users who value design.
• Natural Cycles: The only FDA-cleared contraceptive app. It requires purchasing a thermometer and paying for a subscription. Its algorithm is based on basal body temperature and has high medical accuracy, but it is expensive and requires internet access. Suitable for users with clear contraception or pregnancy-planning needs.

menstrudel.app has a completely different positioning from the products above: it gives up commercialization and feature richness in exchange for absolute privacy and zero cost, making it a top choice for minimalists and privacy-first users.

Final Recommendation

menstrudel.app is best suited to the following scenarios: you are a woman with a technical background, you absolutely cannot accept any health data being uploaded to a server, and you only need the most basic period recording and prediction features; or you have a zero budget and want a free tool with no ads and no in-app purchases. It can also work as a backup app when your main app becomes unusable due to network or privacy issues.

It is not suitable if you need to share data with a partner or doctor, want pregnancy or contraception guidance, prefer a Chinese interface and localized services, or require multi-device sync. In those cases, domestic apps such as 美柚 or paid apps like Flo may be a better fit.

Recommendation: download the installer from GitHub and try it first, then use it long-term only after confirming that the features meet your needs. Since all data is stored locally, it is advisable to manually back up the database file to another device regularly to avoid data loss if your phone is lost or an app update causes problems.