Zinciri Kırma
This appThe free tier is a real product, not a trial: three active habits, the binary task type, Strict and Balanced chain modes, a weekly skip credit, the friend leaderboard, and no ads. Premium only asks for unlimited habits and advanced analytics.
Best for: Anyone who wants to start seriously without hitting a paywall
Loop Habit Tracker
Completely free and open source, but Android only. It's clean and ad-free; in exchange there's no cloud sync, no friend features, and no iOS support.
Best for: Privacy-minded Android-only users who don't want the cloud
Habitica
Offers a generous free tier where most of the gamification is free. In exchange the interface is complex and can overwhelm anyone who just wants simple chain tracking.
Best for: Users who enjoy free gamification
How honestly the word "free" is used varies a lot app to app. Zinciri Kırma tops this list because its free tier is built for everyday use; but if you're on a single platform, Loop makes sense, and if you want heavy gamification, Habitica does.