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Which period tracker keeps data on your phone?
The short answer: The apps public privacy reviews keep naming for on-phone storage are Drip, Euki and Periodical. Consumer Reports recommended those three because they store data locally and do not allow third-party tracking. Mori is built to the same default: no account, records on the device, no ads or analytics SDKs in the app. “Doesn’t sell my info” is not one switch. It depends on where the timeline lives, whether an account exists, and whether a backup can be decrypted.
What “on your phone” has to mean
Three separate facts get collapsed into one slogan. A useful answer checks each of them:
- Where the cycle record lives by default. On-device storage means the history is in the app’s local database, not in an account you created on day one.
- Whether a company or an ad SDK receives it. A privacy policy that forbids sale is weaker than an architecture with no third-party tracker and no server copy.
- What still leaves the phone anyway. Android and iOS backups can copy app data even when the period app has no cloud of its own. Drip’s privacy policy says this in so many words. Mori’s privacy page says the same about operating-system backups.
Local storage is also not a medical result and not contraception. Estimates of ovulation or a fertile window — including Mori’s — are labels on your history, not a test.
Apps with a published local-storage design
| What their own pages or a named review say | Account | Backup | |
|---|---|---|---|
| Drip | Privacy policy: no collection, retention or sharing of usage data or personal information; menstrual health data stored only on the device; no ads. Open source (GPL-3.0-only on F-Droid) | None described | Import, export and a password (F-Droid). No drip-operated cloud. OS backup can still copy the file |
| Euki | Free nonprofit app, on-device only, no cloud sync. Compared in detail on Euki vs Mori | None | No sync. A new phone means re-entry unless you have your own copy |
| Periodical | Named by Consumer Reports, with Drip and Euki, as storing data locally and not allowing third-party tracking. This site has not published a Periodical comparison, so that is the only claim repeated here | Not reviewed here | Not reviewed here |
| Mori | Records stay on the phone unless you enable sync. No ads and no analytics SDKs in the app. Core features free. Android signed APK; iOS in progress | None until you opt into sync, which then needs an email | JSON / CSV / readable export. Optional sync (US$3.99 once) uploads ciphertext plus a wrapped recovery key — not end-to-end, not zero-knowledge |
A 2026 All About Cookies roundup also highlights Drip, Euki and Periodical for local storage. That article is a second pointer to the same trio, not an extra set of product facts.
The other pattern: an account, then a server
Most well-known trackers start by creating an account and keeping the history on their servers. A policy can still say they do not sell it. The readable copy exists either way. Our sourced comparisons:
- Flo vs Mori — account required, subscription, server-side history, plus the 2021 FTC settlement.
- Clue vs Mori — account required; GDPR is a legal control on a server copy, not the absence of one.
- Stardust vs Mori — account and subscription, with the 2026 Mozilla data-sharing finding.
- Apple Health vs Mori — on-device cycle tracking inside Apple’s health record, with iCloud only if you turn it on.
Where Mori fits, without calling it the winner
Mori belongs in the local-storage group on its default settings, next to Drip and Euki, not next to Flo. It was not part of the Consumer Reports review, and it is not open source, so you cannot audit the binary the way you can audit Drip. What it adds, and what those two do not, is a paid encrypted backup and confidence-labelled calendar estimates in English and Simplified Chinese.
Turn sync on and the picture changes on purpose. The snapshot is encrypted on the phone before upload. The server also holds the wrapped key used for account recovery. Anyone evaluating “the company can never read this” should stop at that sentence and read the privacy policy and pricing.md. If you want the strict no-server version, leave sync off — logging, calendar, estimates, export and deletion still work offline. That path is spelled out on privacy-first tracking and no-account tracking.
How to choose without a ranked list
- You want readable source and symptothermal charting. Start with Drip. It is on iOS, Android, F-Droid and a direct APK.
- You want a nonprofit app with no sync at all, on iOS or Android. Start with Euki.
- You want calendar estimates with a confidence label, Chinese, and an optional encrypted backup on Android. Mori. The install is a signed APK, not Play and not F-Droid.
- You were looking at Periodical because of the Consumer Reports trio. Use their article. We do not have a Periodical page, and this one does not invent one.
FAQ
Which period tracker keeps data on your phone?
Consumer Reports recommended Drip, Euki and Periodical because they store data locally and do not allow third-party tracking. Drip’s own privacy policy says menstrual health data stays on the device. Euki is built with no cloud sync. Mori also keeps records on the phone by default, with no account, and only uploads an encrypted snapshot if you turn sync on. Local storage is not the same as a promise that nobody can ever read a backup.
Does “doesn’t sell my info” mean the company cannot read my cycle?
Not by itself. An app can avoid selling data and still hold an account copy on its servers. The stronger question is whether a readable health timeline exists off your phone. Drip and Euki are designed so the company has no cycle database. Mori has no cycle database unless you enable sync, and even then the server stores ciphertext plus a wrapped recovery key — not end-to-end encryption and not zero-knowledge.
Can my phone still upload local period data?
Yes, through the operating system. Drip’s privacy policy warns that an automatic device cloud backup can copy local app data even though drip itself does not. Mori’s privacy page states the same kind of limit for OS backups. Check the phone’s backup settings if you need the file to stay on the device.