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Blitz: Fischer Chess Clock

A minimalist Fischer chess clock for Android.

This app is free software. Its source code is available under the Apache License 2.0.


A chess clock made for blitz

  • Defaults to 5+3 Fischer timing: 5 minutes + 3 seconds per move
  • FIDE-compliant: initial time for 5+3 is 5:03, not 5:00
  • Privacy-friendly: no ads, no permissions

Fast and intuitive controls

  • Touching anywhere on the screen switches to the next player
  • Time and increment are set by horizontal and vertical dragging
  • Haptic feedback is enabled by setting the ringtone to vibrate
  • Back gestures pause and reset the clock

Robust time implementation

  • Uses the most precise time source available on the device
  • Clock implementation tested with 100% code coverage

Free and secure

  • Open source with reproducible builds
  • Enables memory tagging on compatible devices
  • Meets Android 15 security requirements


The app can be installed from four different sources:

  1. F-Droid: built and signed by the developer and verified by F-Droid to correspond to the available source code.
  2. Accrescent: built and signed by the developer.
  3. Play Store: built and signed by Google who can modify the app to optimize its performance, security and/or size.
  4. GitHub: built and signed by the developer but requires Obtainium to update automatically.

As the app is signed using the same private signing key on all sources, it can be updated using a different source to the one it was installed from. For example, an app installed from F-Droid can be updated to a newer version downloaded from the Play Store.

Public key certificate fingerprint


This is a native Android app for Android 5.0+. It is built with Jetpack Compose and implements:

  • Predictive back gestures (Android 14+)
  • Per-app language preferences (Android 13+)
  • Hardware memory tagging (Android 13+)
  • Support for right-to-left languages
  • Precise handling of orientation
  • Keyboard navigation

License: Apache-2.0 — Website — Issue Tracker — Source Code — Changelog — Privacy Policy


 Screenshot of the initial view ​  Screenshot when time is over