The privacy problems hidden in your period tracker

This is the second time [1] that analytics in period apps have been problematic, and also follows the recent hack of MixPanel [2] exposing OpenAI usage data. Seems like 3rd-party analytics are becoming a new frontier for security issues.

[1] https://www.thebureauinvestigates.com/stories/2025-09-03/met...

[2] https://openai.com/index/mixpanel-incident/

I'm male, and clearly don't know enough about this--are there any benefits for the user that a period tracking app can provide by reaching out to the cloud? I guess backing up your data is an obvious one.

I thought entering the information is like 90% of the tracking, everything else is mostly calculation/averaging and none of it needs to live on a server. The Euki app seems like my idea of what it would always be.

Somebody on HN recommended drip awhile ago:

https://f-droid.org/packages/com.drip/

It's not mentioned in the article.

Like Euki it's local-only. I don't know how they compare as far as features but it's cool that there are two good apps out there.

Whenever this issue comes up I feel the need to relay a story about a meeting with a databroker in 1998 who was tracking menstrual cycles using purchasing records of a wide variety of consumer goods. They will track you to optimize their manipulative, targeted advertising whether you have an invasive app or not.

List of recommended ones: https://www.privacyguides.org/en/health-and-wellness/#menstr...

>Drip, Euki, and Apple Health

I use Macrofactor (macro tracking app for lifters with good privacy/UI) as a weight/period tracker, and occasional macro tracker. I don't think anybody is going to go to the effort to hack their databases to find the 100 women tracking our periods on it.

The one downside is that they do days since last period as days since the end of your last period, not days since the start, unlike literally every woman and gynecologist ever.

Apple Health was not among the reviewed?

As others in the thread have pointed out, Euki is a wonderful application and having interacted with members of their team, I know they are committed to maintaining their liberating privacy stances.

What is the privacy concern vs a weight loss tracker?

Only one (of the six reviewed) that I'd call acceptable -

> Euki is the only app Mozilla recommends without reservations. "Euki is special," Wodinsky* says.

> Unlike the other apps on this list, Mozilla says Euki keeps all your health information stored on your device, without even sending it to the company's servers.

> You don't even need to make an account, so you can stay completely anonymous. Euki also offers a "decoy" feature that shows fake, harmless information if someone gets your phone and tries to snoop.

*Shoshana Wodinsky, a privacy research analyst who tested 6 period tracker on behalf of the Mozilla Foundation

Why not something p2p and encrypted? https://peerloomllc.com/pearpetal/ No servers, no problem. You fear losing your device? I'm sure you have more than one, any additional one you have is a fully functional backup.

The technology it is built on is extremely cool. http://pears.com/

Or better yet. Why trust this one (even though the source is on github)? You can just ask your AI agent to build you your custom one on the basis of this technology.

Period trackers are the perfect usecase for homomorphic encryption, where the system can operate on the data without knowing what the data says. It's slow and has a lot of overhead, but it's an active area of research. That way, the platform doesn't know what you're telling it. You have to trust the platform to have implemented it properly, and it's rather nerdy a detail, so it's no surprise there isn't one yet.

RudderStack founder here.

Although the article doesn't accuse us of doing anything improper, we weren't contacted for comment, so I'd like to clarify our role.

We are customer data infrastructure, not a data broker. We do not buy, sell or monetize the customer data that passes through our systems.

Our role is analogous to infrastructure: customers choose what data to send, and RudderStack routes that data to the destinations they configure (analytics tools, data warehouses, marketing platforms, etc.). The customer owns the data and decides where it goes; RudderStack does not repurpose it for its own business.

Infrastructure providers like us should be held to high standards for security and privacy, but we should not be confused with companies that collect or monetize end-user data.