Interval Apps

Free, open-source interval timers for Android and the web. No ads, no account, no tracking. Works offline.

The apps

Tabata Timer

The classic protocol — 20 s of work, 10 s of rest, 8 rounds — with every number adjustable.

Web · APK preview · RuStore

Japanese Walking

Interval walking: 3 minutes fast, 3 minutes slow, 5 times — a 30-minute session. On Android, plays your own music for each pace and keeps going with the screen off.

Web · APK preview

Both apps

Both apps speak English and Russian, play a sound when the phase changes, keep the screen on while the timer runs and come in a light and a dark theme that follows the phone until you pick one. Phase changes also tap back with a vibration you can turn down or off in the settings.

APK preview links point to test builds of the latest main. They install next to the store versions as separate "Preview" apps and update each other.

Why a monorepo

The two apps are separate products with their own store listings, but they share almost everything underneath:

flowchart LR
  core["interval_core<br><sub>pure Dart engine</sub>"] --> kit["interval_kit<br><sub>theme · widgets · cues · app shell</sub>"]
  kit --> tabata["apps/tabata"]
  kit --> media["interval_media<br><sub>music · media session</sub>"]
  media --> walking["apps/walking"]
  testing["interval_testing<br><sub>test helpers</sub>"] -.-> tabata
  testing -.-> walking

Path	Contents
packages/interval_core	The workout engine: plans, phases and a timer that never drifts. Pure Dart, no Flutter.
packages/interval_kit	Everything the apps share on screen: theme, widgets, sound cues, the workout screen and the app shell.
packages/interval_media	Music per pace with cross-fades, and the media session that keeps a workout running with the screen off. Only the walking app uses it.
packages/interval_testing	Helpers for widget tests and README screenshots.
apps/tabata	The Tabata timer. Settings and phase names only.
apps/walking	The Japanese walking timer. Settings, phase names and the music screens.

A fix in the engine or a widget lands in both apps with the next build. Read more in the architecture notes.

Getting started

You need Flutter 3.47 — the exact version is pinned in pubspec.yaml — and, for Android builds, the Android SDK.

git clone https://github.com/manul-wizard/interval-apps.git
cd interval-apps
flutter pub get          # resolves the whole workspace at once

cd apps/tabata           # or apps/walking
flutter run -d chrome    # or pick an Android device

Everyday commands

Task	Command
Format	dart format .
Analyze everything	flutter analyze
Test the engine	cd packages/interval_core && dart test
Test a Flutter package or app	cd <dir> && flutter test
Regenerate screenshots	cd apps/<app> && flutter test --tags screenshots --run-skipped
Regenerate launcher icons	cd apps/<app> && dart run flutter_launcher_icons
Build a release	cd apps/<app> && flutter build apk / flutter build web

CI runs the same checks on every pull request; see CONTRIBUTING.md for the workflow.

History

The Tabata timer started as a Unity project. It was rewritten in Flutter to get a much smaller app, a faster web version and native audio features the walking app needs. The design, sounds and settings carried over unchanged.

Contributing

Bug reports, ideas and pull requests are welcome — start with CONTRIBUTING.md. Please follow the code of conduct, and report security issues privately as described in SECURITY.md.

Credits and license

Sounds come from Freesound and the font is Ubuntu; authors and licenses are listed in CREDITS.md.

The code is licensed under the Apache License 2.0.