I guess it's really safe cause it's open source, you can make notes on your habits but don't really do that. Its simple. Really fast. Haven't found a way to connect it to notion. In general it's a great app to track you habits. Does its job. Not more, not less.
Karma Smart Habit Tracker - A new way to track your habits from the browser 🎯✅
Habitica - Habitica is a free habit building and productivity application.
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Notion Minimalist Habit Tracker - Create, track and reflect on your habits
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.