HabitKit

HabitKit is a habit tracker for iPhone and Android built around a year-long heatmap grid. You name a habit, pick the color its tiles will fill, tap once to log today, and each day fills a tile so the grid becomes a visible chain. A missed day is simply an empty square.

Setup takes three steps, and forgotten days can be filled in later from the habit's calendar. The app offers home screen widgets, overview layouts as cards, checklist or compact, hundreds of icons and 30+ colors, stats on completions, rates and streak records, goals such as three times a week or 20 times a month, and shareable streak cards. It works for building good habits or quitting bad ones.

The app is free on both stores, private, needs no account and sends reminders only if you ask for one, and the site adds a guides section and reviews from app store users. It targets people who want a visual, low-effort log of workouts, reading, water or smoke-free days.