Every free period app has the same problem. The product is given away, and something else has to pay for the engineering, the servers, and the staff. When that something else is advertising, the product stops being the cycle tracker and starts being the user.
We did not want to make that product. So we did not.
What advertising requires
An advertising business needs three things to function. It needs to identify users, so it can show different ads to different people. It needs to predict their behaviour, so it can charge advertisers for high intent moments. It needs to measure outcomes, so advertisers will keep buying.
All three of those needs translate directly to data collection. Identification means tracking. Prediction means profiling. Measurement means cross device, cross context, cross app surveillance. None of that is compatible with the kind of privacy a women's health app should offer.
You can build an ad supported product that calls itself private. You cannot build one that actually is.
Why "we only show contextual ads" is not an answer
There is a softer version of ad supported business that some apps reach for. They claim they do not target individuals, only context. They argue that this is privacy preserving.
It is not. Even contextual advertising requires the app to broker a connection between the user's device and the ad network's servers. That connection itself carries data. The ad network knows what app the user is in, what country, what time, what device, what frequency. Stitched together with the same signal from other apps, that data identifies and tracks the user, regardless of what the app itself claims to be doing.
The only ad model that is genuinely privacy preserving is no ads. We picked that one.
How we pay for the work
The honest answer is that V1 is funded by the founders' own savings, the support of a small number of angel investors who share the long term thesis, and a future paid tier that will offer additional features without putting any of the V1 functionality behind a paywall.
Cycle tracking, daily logging, predictions, exports, doctor visit PDFs, all 18 languages, app lock, stealth mode, and legal protection mode are free in V1 and will stay free. We do not believe a woman should pay to have access to her own body's data.
The paid tier, when it ships, will be additive. It will cover things like advanced pattern analysis, longer history features, family planning specific tools, and similar capabilities that are valuable to people who want them and ignorable for people who do not. It will not change anything about how the core app handles privacy.
The structural commitment
Saying "we will never have ads" is a marketing statement. Building a company where ads are not possible is a structural one. We aim for the second.
That means we have not integrated any ad SDK, even one that is dormant. We have not negotiated future deals with ad networks. We have not signed contracts that include data sharing clauses. We have built the production binary so that there is no advertising surface to turn on.
If a future investor or acquirer wanted to add advertising to mylune, they would have to substantially rebuild the architecture. That is the friction we want. The harder it is to break the promise, the more meaningful the promise is.
A note on incentives
The simplest way to predict how an app will behave is to ask who pays for it. Apps paid for by ads will, over time, optimise for the advertiser. Apps paid for by users will, over time, optimise for the user.
We chose the second model deliberately, because we want the work to drift toward serving the woman holding the phone, not toward proving conversion to a buyer who never opens the app.
The cost of that choice shows up on our side of the table, not yours.