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Zero vs FastTrack: catalog facts
Zero	FastTrack
Freemium Free to download, with a paid subscription for additional features.	Free Free and open source under the MIT licence, with no ads or in-app purchases.
Android, iOS	Android
One-tap fasting timer Meal logging by photo or text description	No ads, purchases or permissions Shows what the body is doing at each stage of a fast
Mobile only, no web version Less detailed nutrient tracking than full calorie counters	Android only Not a medical app
Downloadable app	Downloadable app
Closed source	Open source
License not stated	License: MIT
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 Checked September 23, 2026	Official website Full listing and sources Checked October 2, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.