Flo is one of the most popular period and cycle tracking apps available, with 77 million monthly active users and over 300 million downloads worldwide. For most people looking to track their menstrual cycle, it’s a solid choice with a generous free tier, but it comes with some important caveats around privacy history and the limits of its premium upsell.
What You Get for Free
The free version of Flo covers the basics that most people actually need from a cycle tracker. You get period and ovulation predictions, symptom tracking, a full cycle history, and access to a health library covering pregnancy, general health, and LGBTQ+ sexual and reproductive health topics. There’s also an anonymous community chat forum where you can ask questions and read discussions from other users.
Day to day, you can log your period start date, symptoms, sexual and physical activity, mood, diet, discharge details, and results from pregnancy or ovulation tests. A “Today” tab gives you quick resources tailored to where you are in your cycle. The free version also includes Anonymous Mode, a privacy feature that strips your personal identifiers from your health data (more on that below).
For someone who simply wants to know when their next period is coming and keep a record of symptoms over time, the free version does the job without feeling stripped down.
What Premium Adds
Flo Premium unlocks a virtual health assistant that generates detailed cycle reports and flags possible signs of conditions like PCOS and endometriosis. You also get more detailed pregnancy tracking, daily health insight stories, video courses, and expanded symptom predictions.
One feature that stands out is partner linking, which lets someone else see where you are in your cycle, your possible symptoms, and your chance of pregnancy. This can be useful for couples trying to conceive or for partners who want to be more aware and supportive.
Whether Premium is worth paying for depends on what you’re using the app for. If you’re actively trying to get pregnant or want deeper insights into cycle patterns, the extra features add real value. If you’re just tracking periods, the free version is enough.
How Accurate Are the Predictions?
Flo’s period and ovulation predictions rely on the data you feed it, which means accuracy improves the longer you use the app. For the first few cycles, predictions can be off by several days, especially if your cycle length varies. This is true of all algorithm-based trackers, not just Flo.
It’s worth being direct here: no app can pinpoint ovulation with the precision of methods like basal body temperature tracking or ovulation test strips. Flo’s predictions are estimates based on cycle length patterns. If you’re relying on the app for fertility planning in either direction, treat its predictions as a starting point rather than a guarantee.
The Privacy Question
Privacy is the area where Flo has the most complicated track record. In 2021, the Federal Trade Commission settled allegations that Flo had shared users’ health information with outside data analytics providers, including Facebook and Google, after promising that data would be kept private. That’s a significant breach of trust for an app that collects deeply personal health information.
Since then, Flo has made substantial changes. The app now holds dual ISO 27001 and ISO 27701 certifications, internationally recognized standards for information security and privacy management. Flo is the first period tracker to achieve both. All data is encrypted as standard.
The most meaningful privacy addition is Anonymous Mode, which separates your health data from any personal identifiers. When you switch it on, the app creates a new account that doesn’t contain your email address, Apple or Google account ID, payment information, IP address, or advertising identifiers. Your cycle data transfers over, but nothing that ties it to your identity does. The design ensures that no single party processing your data can connect who you are with what you’re tracking.
This matters particularly for users in places where reproductive health data could carry legal risks. Anonymous Mode doesn’t require a premium subscription.
Medical Credibility
Flo’s content is backed by an 18-member scientific advisory board that includes faculty from Yale School of Medicine, Mayo Clinic, Johns Hopkins, and University College London. The board spans obstetrics and gynecology, psychiatry, cognitive neuroscience, health informatics, and public health. Educational content comes in multiple formats: articles, quick tips, FAQs, video courses, and expert discussions.
This level of medical oversight puts Flo ahead of many competing apps that rely on generic wellness content without clear expert review. That said, the app’s health insights are educational, not diagnostic. Flagging possible signs of PCOS or endometriosis is useful for prompting a conversation with a doctor, but the app isn’t making a clinical assessment.
Where Flo Falls Short
The most common frustrations with Flo tend to center on the premium upsell. The app regularly nudges free users toward a subscription, and some features that feel like they should be part of the core experience are locked behind the paywall. The boundary between “free” and “premium” can feel arbitrary at times.
The sheer volume of content can also be overwhelming. Between articles, community chats, health insights, playlists, and music, the app tries to be an all-in-one wellness platform rather than a focused cycle tracker. If you prefer a clean, minimal interface, Flo’s busy design may not appeal to you.
And despite the improvements, the FTC settlement is recent enough that some users remain uncomfortable trusting any period tracking app with sensitive data. If that’s you, Anonymous Mode helps, but it requires you to trust the technical implementation of a company that already broke that trust once.
How It Compares Overall
Flo is a good app for most people who want a feature-rich cycle tracker with solid educational content and strong medical backing. The free version is genuinely useful, the privacy infrastructure has improved dramatically, and the sheer size of its user base means its prediction algorithms benefit from a large data set. It’s particularly strong for people who want pregnancy tracking or health education alongside basic cycle logging.
It’s not the best choice if you want a minimalist tracker, if you’re uncomfortable with its privacy history, or if aggressive premium prompts bother you. Apps like Clue offer a cleaner, more data-focused alternative, though with their own tradeoffs in features and pricing. For fertility-specific tracking, dedicated apps that integrate with basal body temperature devices tend to be more precise than any algorithm-only approach.