Why I read fourteen privacy labels in one sitting

Short version: I read the App Store privacy label of every significant period tracker I could find — fourteen of them — and wrote down exactly what each one declares. Seven say they use your data to track you. Two collect nothing at all. Mine is neither the worst nor the best, and I published it that way. The result is the Period Tracker Privacy Index.

Why I did it

It started as a defensive exercise, which I’m slightly embarrassed by. Someone asked me how Dew compared to the big trackers on privacy, and I gave the answer I always give — that Dew keeps your cycle on your phone, that there are no servers, that there’s nothing for me to sell even if I wanted to. All true. All also exactly what every other app’s marketing page says about itself, in more or less those words.

I realised I was asking people to take my word for it in a category where taking a company’s word for it is precisely the thing that has gone wrong before. Flo told its users their data was private, and in 2021 settled FTC allegations that it had shared that data with third parties anyway. No fine, no admission. But the promise and the practice had come apart, and users had no way to see it.

So the question became: is there anything here that isn’t a promise?

There is, and it had been sitting in plain sight. Every iOS app has to declare to Apple what it collects, and Apple publishes that declaration on the product page. It’s self-reported, and Apple doesn’t audit it — I’ll come back to that limit. But it’s a public, on-the-record statement with consequences if it’s false, which is a meaningfully different object from a marketing claim. And nobody in this category seemed to have simply written them all down in one place.

What it was like

Genuinely tedious, and then abruptly not.

The mechanics were dull. Apple renders the privacy label into a structured blob on each product page, so I pulled each listing and read the declaration out of it directly rather than squinting at screenshots. Fourteen apps. About an hour, most of it spent making sure I was reading the right field and not something that merely looked like it.

The part that stopped me was the tally. I had expected the big ad-supported trackers to show up badly — that isn’t news to anyone. What I hadn’t expected was seven of fourteen declaring “Data Used to Track You.” Not “collects analytics.” Not “shares with partners.” Apple’s specific category for linking your data with data from other companies for advertising, or handing it to a data broker. Half the category, in their own words, on their own listings.

Nine of them link your health and fitness data to your actual identity. Eight do it with data Apple classifies as sensitive.

None of this is hidden. It is one tap down from the Install button on every single one of those apps. It is just that almost nobody taps.

The part I didn’t enjoy

I put Dew in the table, because an index that quietly omits its author’s own product is worthless. Then I had to decide what to do when it didn’t win.

Euki and drip both declare “Data Not Collected.” Nothing. Dew declares “Data Not Linked to You” for Usage Data and Diagnostics, because Dew sends an anonymous, opt-out counter that tells me how many people opened the app — never cycle data, never anything identifying. I think that’s a defensible trade-off and I’d make it again; it’s how I know whether a feature works at all.

But defensible isn’t the same as best, and by the measure I chose, it isn’t best. Euki and drip are stricter than Dew. Euki is the only period app Mozilla named to its “Best Of” category. drip is open source, which means you don’t have to believe anyone — you can read it.

I sat with that for a while, mostly wondering whether to add a column that would have made Dew look better. There were a few candidates. That instinct is exactly why almost every comparison table published by a company is useless, and noticing myself have it was the most useful thing that happened all day.

So the ranking stands as the data left it. If the strictest possible answer is what you want, it isn’t my app, and you should know that from me rather than from someone else later.

What the index can’t tell you

The honest limit, stated where you can’t miss it: these labels are developer-declared, and Apple does not audit them. The index reports what each app says it does.

That is worth more than nothing and less than an audit. A public declaration is checkable and carries consequences if false — the FTC case against Flo was about exactly that gap between statement and practice. But it is a statement, and I’d rather readers hold it as one than mistake this for something it isn’t.

It is also perishable. Apps change their declarations. Every row carries the date it was read, and a row is only as good as that date.

Use it

The index is here, published under CC BY 4.0. Quote it, republish it, take it apart. If you find a mistake — a label I misread, a row that’s gone stale, an app I should have included — email [email protected] and I’ll fix it and say that I did.

The thing I’d actually like you to take from it isn’t which app to install. It’s that the answer was public the whole time, on a page you’ve already visited, one tap from a button you’ve already pressed. It takes thirty seconds to check before you install the next thing. That habit will outlast any table I make.

If you want the longer story of why I built a period tracker at all, that’s in why I built Dew.