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Periodical vs Flo: catalog facts
Periodical	Flo
Best for: Android users who want a private, open-source period calendar	Best for: People tracking their menstrual cycle, ovulation or pregnancy on a phone
Free Free and open source under the GPL-3.0-or-later licence.	Free + paid options Free to download, with a paid premium subscription.
Android	Android, iOS
Calculates fertile days and tracks symptoms and notes Backup to a single compressed file on local storage All 4 strengths for Periodical Calculates fertile days and tracks symptoms and notes Backup to a single compressed file on local storage Available from F-Droid, Google Play or as an APK Translated through a community Crowdin project	Tracks periods, ovulation and pregnancy in one app Symptom logging alongside cycle dates
Calendar method is not reliable for contraception Simple feature set compared with commercial cycle trackers	Proprietary service that handles sensitive health data Some features require a paid subscription
Downloadable app	Downloadable app, Hosted service
Open source	Not open source
License: GPL-3.0-or-later	License not stated
Not stated if an account is needed	Not stated if an account is needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Sources for Periodical arnowelzel.de/projekte/periodical f-droid.org/packages/de.arnowelzel.android.periodical Catalog checked October 2, 2026	Official website Full listing and sources Sources for Flo flo.health play.google.com/store/apps/details apps.apple.com/us/app/flo-cycle-period-tracker/id1038369065 Catalog checked September 23, 2026

“Not stated” means we have not confirmed it. Features can vary by device and plan.