Is my period tracker data private?

What should I check before trusting a period tracker?

Five questions tell you most of what you need. None needs technical knowledge.

• Does it work without an account? No account means nothing ties your cycle to your name or email.
• Where do your logs live by default? On your phone is the safest answer. On a company server, it matters who holds the key.
• Is sync end-to-end encrypted? If the company cannot read it, it cannot share it or lose it in readable form.
• Does it say exactly what the server can see? A specific public list beats a slogan such as “your data is private”.
• Has anyone independent tested it? Mozilla’s Privacy Not Included and Nothing Personal reviews test what apps really send.

What have independent reviews found?

Sources differ in scope and date, so read them as snapshots rather than a ranking of today.

How does Splash handle my data?

Splash saves your cycle on your phone. If you never make an account, nothing about your cycle reaches us. If you turn on backup, sync or partner sharing, your phone encrypts the data with AES-GCM-256 first and we store only a locked copy with no key.

With an account, our server can see your email, when you sync and how big the locked copy is, which categories a partner share includes, push notification addresses and the neutral text of notifications. It cannot see your logs. There are no analytics SDKs, trackers or data sales. The full list is on the privacy page.

Splash has not been independently tested by Mozilla yet, and we say so. Euki is open source, which lets anyone audit it; Splash is not.

What can I do today to protect my cycle data?

• Lock the app with a PIN, Face ID or fingerprint, and consider a decoy PIN that opens an empty app.
• Turn on discreet mode if someone might glance at your screen or notifications.
• Check app permissions in your phone settings, and turn off location, contacts and ad tracking for health apps.
• Back up with an encrypted option or a file you keep, not an unlocked cloud folder.
• Delete the account when you leave an app, and ask for your data to be erased. Splash’s delete removes every row we hold.

Questions people ask

Do period tracker apps sell your data?

Practice varies. Many share data with analytics or advertising services, and a few have been caught sending sensitive details. Mozilla’s July 2026 review of six trackers found only Stardust sending health data to another company. Splash does not sell data and has no analytics SDKs, and without an account nothing about your cycle reaches us.

Is Flo safe to use?

Flo has a free Anonymous Mode and has changed its practices since its 2021 FTC settlement. Mozilla’s July 2026 review scored it 7 out of 10 and reported no health data shared with advertisers, analytics or marketing partners. Read its privacy policy and decide what you are comfortable with.

Which period tracker is the most private?

Euki is the most private tracker we can source: open source, run by a non-profit, data only on your device, and 10 out of 10 in Mozilla’s July 2026 review. drip is similar. Splash is local-first with optional encrypted sync and sharing. Apple Cycle Tracking is end-to-end encrypted in iCloud with two-factor authentication.

Is a paper diary more private?

A paper diary has no servers, but it is only as private as where you keep it, and it cannot predict or summarise. If you prefer an app, choose one that works without an account and locks with a PIN. If you share a phone, use a decoy PIN and discreet mode.

Sources

1. Digital Health: ORCHA research identifies privacy issues with period tracking apps (29 Jul 2022) accessed 2026-10-28 (Read through a search excerpt.)
2. Mozilla Foundation: In post-Roe era, Mozilla labels 18 of 25 popular period and pregnancy tracking tech with a Privacy Not Included warning (Aug 2022) accessed 2026-10-28 (Mozilla’s page blocks automated fetching; read through search excerpts.)
3. Mozilla Foundation: Nothing Personal, period and ovulation trackers (16 Jul 2026) accessed 2026-10-28 (Mozilla’s page blocks automated fetching. The findings used here are checked against the two reports listed next to it.)
4. DH Insights: Mozilla report reveals wide privacy gaps among popular period tracking apps (30 Jul 2026) accessed 2026-10-28
5. TechCrunch: Period tracker Stardust shares users’ health data with analytics firm, says Mozilla research (16 Jul 2026) accessed 2026-10-28
6. FTC: FTC finalizes order with Flo Health (22 Jun 2021) accessed 2026-10-26
7. FemTech Insider: California jury rules Meta violated privacy laws in Flo Health data case (6 Aug 2025) accessed 2026-10-28
8. Flo: Anonymous Mode FAQ accessed 2026-10-26
9. Apple Support: Track your menstrual cycle (Cycle Tracking), published 14 Sep 2026 accessed 2026-10-28
10. Euki (official site) accessed 2026-10-26

Splash makes one of the apps mentioned here, so every claim about another app links to its own page or an independent source. Spotted something wrong? Email us and we will fix it and note the change.

Keep reading

• What Splash can and cannot see
• Is Flo safe? Period app privacy, dated
• Best private period tracker apps
• Privacy features
• If someone checks your phone
• What is the best period tracker for irregular periods in the UK?
• Is there a period tracker that works without an account?
• How accurate are period tracker predictions?
• Which period tracker is best for perimenopause?

General information, not medical advice. Splash is not contraception, not a medical device and cannot diagnose, and it is not affiliated with the NHS. If you are worried, talk to a GP, pharmacist or sexual health clinic. How we write and check content.