Period Tracker Without a Subscription: What Free Actually Costs

You can track a cycle properly without paying for anything, so the useful question is not whether an app costs money but who pays for it and how. Every way of funding software leaves a fingerprint on the product. Money from you points the app at you. Money from donors or a grant points it at a mission somebody wrote down. Money from advertisers points it at whoever is buying attention, and that is the one arrangement in which your data has a job to do. "Free" is not a property of an app. It is a description of one side of a transaction, and it is worth knowing the other side before you hand over a year of your life.

There are five ways a period tracker gets paid for, and only one of them involves a subscription. What follows is each of them, what its incentives look like, and how to work out which one you are holding.

Why this page quotes no prices

Not squeamishness. Prices move, they differ by country, and they differ between the two stores. Any figure printed here would be wrong for some readers on the day it was written and wrong for everybody within a year, and a stale number about somebody's money is worse than no number. The store listing is the only current record of what an app costs, which is where that question belongs.

What a company publishes about how it is funded is a different sort of statement. It is durable, it is the company's own words, and it can be quoted without going out of date next quarter. That is what this page uses, and it is the only thing about a named app you will find below.

When you are the customer

Software you pay for, whether by a one-off purchase or a subscription, has the simplest incentive on the list: it has to stay worth having, because you can stop. The company's revenue does not depend on anything happening to your cycle data, and that is a genuine structural comfort rather than a slogan.

Two honest qualifications. Paying does not make an app private. It removes one motive for moving your data, not the ability to move it, and a paid app can still hold an account, keep a server copy and send analytics like any other. And a subscription changes the relationship in a way a one-off purchase does not: the thing you are relying on is a payment you have to keep making, and if it lapses you should know in advance whether your history stays readable. That is the difference between a promise and an architecture, which is the whole of what actually makes a tracker private.

When donors pay

Euki describes itself as an open-source project managed by an independent 501(c)(3) nonprofit, funded by community support and donations, free to use with no paywalls, and states that because it never collects personal data it does not sell it or use it to target advertising. That is the company describing itself, which is the only way this site will describe anybody.

What makes that description unusually checkable is that both halves of it leave a public trace. A registered nonprofit's funding is a matter of record, and open source means the code can be read by somebody who knows how. You are not being asked to take the privacy claim purely on trust, which is more than most of this market offers.

The weakness of the model is not dishonesty. It is that donations and grants arrive in cycles, and an app that costs money to maintain has to keep winning them. Ask the same question you would ask of any small company: if the money stopped, what happens to the app on my phone, and can I get my data out of it?

When nobody is paid

The strictest version of free is a project people build in their own time and give away. The drip privacy policy states that there is no collection of usage data or personal information, no ads and no spyware; that menstrual cycle data is stored locally on the device and cannot be accessed by other apps; that deleting the app data in settings or uninstalling it removes that data; and that the source code can be read to check that all of this is true. It adds that an automatic cloud backup may still take place depending on your device settings, which is the kind of caveat marketing departments do not write.

The risk here is the one nobody puts on a comparison chart: volunteer projects can go quiet. Nobody is contractually obliged to fix anything, releases depend on somebody's spare weekend, and a phone software update can break an app that has no paid maintainer to catch it. That is not an argument against using one. It is an argument for exporting your history regularly and knowing where the file is, and it is covered further in what open source actually guarantees in a period tracker.

When the phone has already been paid for

There is a tracker built into the iPhone, and its funding model is that you bought a phone. Apple's guide says you can log menstrual cycle information in Health to get period and fertile window predictions, and that the log covers period days, flow level, symptoms, spotting, basal body temperature and more; it says an Apple Watch can be used to help log it, and that on supported models Siri can log a period start.

Nothing to pay and nothing to sign up for, and the trade is straightforward: you get the features the platform decided to build, and if you want something it does not do, there is nobody to ask. For a lot of people that is a fair deal, and what the built-in Cycle Tracking covers is worth checking before installing anything else.

When an advertiser is the customer

The last model is the one the other four are usually being contrasted with, and it deserves plain description rather than alarm. If an app is free, carries no visible way of being paid for, and shows advertising, then somebody buying attention is the customer and your data is the product being refined. That does not mean anything illegal is happening. It means the incentive points away from you, permanently, and no policy wording changes the direction it points.

For scale rather than accusation: a peer-reviewed scoping review of health apps found that most of those examined — 20 of 23 — shared user data with third parties. That is health apps in general, not period apps in particular, and it is the category this genre sits inside.

The counterweight belongs in the same breath. When the UK's Information Commissioner's Office reviewed period and fertility apps in 2024, it reported that no serious compliance issues or evidence of harms were identified, while urging developers to prioritise privacy. And the legal backstop is thinner than most people assume: the US Federal Trade Commission's own guidance says that many companies collecting health information — a fitness tracker, a diet app, a connected blood pressure cuff — are not covered by HIPAA at all, and that the FTC Act and the Health Breach Notification Rule apply instead. Real protection, but mostly the kind that tells you after something has gone wrong. The mechanics of that model are the subject of why the business model is the feature.

Working out which one you are holding

Five questions, answerable from the store listing and the app's own settings screen before you log anything.

• Is there anything to buy inside the app, and does the listing say so?
• Does the app show advertising, and does its store label declare tracking?
• Is there an account, and therefore a server copy?
• Does the company say anywhere who funds it, in its own words?
• Is the source code public, so that somebody could check the claims?

If four of those come back blank — no purchase, no ads, no stated funder, no code — that blankness is itself the answer. Somebody is paying for the servers, and you have not been told who.

It is also worth remembering how little of this needs software at all. Predicting a period is arithmetic on your own recent start dates: the cycle length calculator works out your average and how much it moves, and the period calculator turns that into a window with the uncertainty printed beside it. Both run in your browser and cost nothing because there is nothing to run. If you would rather own the whole thing outright, the printable period tracker is a sheet of paper with no funding model whatsoever.

Where Athena stands

Athena is the app this site is being built for, and it has not been released. It is in no store, nothing here is for sale, and there is nothing to sign up for. The tools above are the working product today.

The plan, in the plainest words available: the core tracker stays free, and an optional upgrade will add deeper analysis for anybody who wants it. The essentials are not the part that gets locked away. Cycle data will be written to a private database on the phone and predictions calculated on the device, with no account and no server copy of health data. Two things do leave the device and it would be dishonest to imply otherwise: anonymous diagnostics to Firebase — features used, crashes, device model, never anything you log — and, on this website, IP-anonymised web analytics that count visits. The limitation of building it this way is real: no account means no automatic backup, so if the phone is lost and nothing was exported, the history is gone.