Free is a price tag, not a business model
Downloading costs nothing, signing up costs nothing, the first few weeks cost nothing. But building and running software isn't free. Somewhere in the accounts there is income – you just can't see it when you download.
For you this isn't an academic question. The business model decides which feature sits behind a paywall, how often you are nudged towards a subscription and what happens to what you log.
The four usual models
- Advertising. The app is free and shows ads. So that they can be targeted, device identifiers and usage behaviour usually go to ad networks.
- Freemium with a paywall. The basics are free, the useful parts – analysis, symptoms, export, reminders – sit behind “Premium”. The free version is then less a product than a sales floor.
- Subscription with a trial. Seven days free, then an annual subscription runs that you need to cancel in time. Only the beginning was free.
- Data as a product. The most sensitive model: usage or health data is analysed, enriched or passed on. What exactly happens is found, if anywhere, in the privacy policy under “sharing with third parties”.
None of these models is wrong in itself. Charging for work is more honest than hiding it. It only gets uncomfortable when the store listing says “free” and the real bill arrives later.
Why this matters more for cycle data
A cycle diary isn't a step counter. It records when you bleed, how you feel, whether you had sex, whether you want to get pregnant. The EU's GDPR therefore treats health data as a special category (Art. 9): it may only be processed with your explicit consent.
In practice this means looking more closely at a period app than at a torch app. Not because every provider means harm, but because the damage is greater if something goes wrong.
The five-minute test
You don't have to take anyone's word for it, including ours. You can check these points for any app yourself:
- Read the store listing. Below the price, Apple notes “In-App Purchases”, Google also “Contains ads”. If neither is there, there is no subscription and no advertising.
- Open the privacy label. Apple's “App Privacy” and Google's “Data safety” list which data is collected and whether it is shared with third parties. The information comes from the provider, but it is binding.
- Look for the paywall. Open analysis, export and settings. Where a lock or a star appears, the free version ends.
- Switch on flight mode. If the app keeps working, your data is on the device. If it stays empty or asks for a connection, it is on someone else's server.
- Check whether an account is required. Without registration there is no identifier under which your entries could be linked to your name.
- Check the exit. Can you export your data and delete it completely without having to write an email? If not, it is harder to get out than to get in.
How Rhythmus is funded
The details – no account, no subscription, no ads, no data sharing – are on this page (in German), together with what this model costs us.
In short: it isn't. Rhythmus is a passion project, not a company. There are no ads, no in-app purchases, no subscription, no premium tier and no feature we are holding back for a later paid version. The same is stated in our legal notice, where we are liable for it.
This is possible because the app costs almost nothing to run: it has no backend. Your entries are stored in your browser, not in our database – we don't run one. There is no registration, no analytics software and no tracking; we even ship the fonts ourselves instead of loading them from other servers. What's left is delivering a few program files.
That has a side effect that matters more to us than the price: we have nothing to sell. So we don't have to claim effects the evidence doesn't support – see our article on cycle-based training, where we assess the evidence for our own concept.
What this model costs you
Honesty works both ways. Without a server you also don't get what servers can do:
- No sync. Your data lives on the device where you entered it – not on the tablet next to it.
- Browser data deleted means data gone. We can't restore anything because we never had anything.
- You make the backup. Under Settings → Download backup you get a file with everything in it. Keep it somewhere you'll find it again.
- No support team. There is an email address, and behind it are we.
What it comes down to
“Free” on its own says little. The more useful question is how an app makes money and what it needs from you in return. For some the answer is a subscription, for others your attention, for others your data. For us it is: nothing – but the backup is up to you.