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KazumaProject/JapaneseKeyboard

A fully offline Japanese input keyboard for Android, built on Google's mozc engine with user dictionaries, snippets and custom layouts.

Open-source alternative to:GboardGoogle Japanese Input

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369
Forks
41
Open issues
29
Last commit
9 hours ago

What is it?

Sumire (スミレ) is an Android Japanese input method that performs all keystroke-to-candidate conversion on the device. The app does not request the INTERNET permission, so typed text is not sent to any server. Conversion uses a dictionary from the open-source mozc engine, with an LOUDS trie dictionary and an N-gram model used for ranking.

Beyond standard kana input, the keyboard offers a user dictionary with forward-matching predictions and import/export, plus snippets triggered by exact-match readings. Users can define their own key layouts through a custom keyboard mode. Other modes include TenKey, a 50-on layout, QWERTY English and romaji input, and a floating window display. An optional formula candidate feature renders simple expressions and LaTeX as Unicode text or normalized LaTeX.

The project is written in Kotlin and supports phones and tablets. Full and Lite builds are published on Google Play, F-Droid and GitHub Releases, and the Full build bundles the zenz and Gemma model components.

Key features

  • 01Runs entirely on-device and requests no INTERNET permission.
  • 02Uses the mozc dictionary and N-gram ranking for kana-to-kanji conversion.
  • 03User dictionary with forward-matching predictions and import/export.
  • 04Snippets triggered by exact-match readings, with import/export.
  • 05Custom keyboard layouts that users define themselves.
  • 06Multiple input modes including TenKey, 50-on, QWERTY romaji and floating window.

Use cases

  • Typing Japanese on Android without sending keystrokes to a cloud service.
  • Keeping a personal dictionary and frequently used phrases that can be backed up and moved between devices.
  • Building a keyboard layout tailored to one's own typing habits.
  • Using a Japanese keyboard on tablets or foldables.

Quick start

  1. 1

    Install the app from Google Play, F-Droid (Lite build), or the GitHub releases page

  2. 2

    In Android settings, open the on-screen keyboard list and enable Sumire

  3. 3

    Clone the repository to build from source

    git clone https://github.com/KazumaProject/JapaneseKeyboard.git
  4. 4

    Build and install the debug app on a connected device or emulator

    ./gradlew installDebug

Things to know

  • Android only; this is a keyboard app for Android devices.
  • Building from source needs Android Studio, the Android 17 (API 37) SDK, and network access to fetch the Zenz model from Hugging Face.
  • Some features such as the AI Zenz and Gemma options are only in the Full build and add to the app size.

In collections

Privacy & local-first toolsAndroid apps & phone tools

Topics

#japanese-input#android#keyboard#ime#offline#privacy#kotlin#japanese-kana

FAQ

What is JapaneseKeyboard?
A fully offline Japanese input keyboard for Android, built on Google's mozc engine with user dictionaries, snippets and custom layouts. Sumire (スミレ) is an Android Japanese input method that performs all keystroke-to-candidate conversion on the device. The app does not request the INTERNET permission, so typed text is not sent to any server. Conversion uses a dictionary from the open-source mozc engine, with an LOUDS trie dictionary and an N-gram model used for ranking.
Is JapaneseKeyboard free to use? What license does it have?
JapaneseKeyboard is open source under the MIT license. Check the license terms before using it in commercial products.
Is JapaneseKeyboard still maintained?
Actively maintained. The last commit to JapaneseKeyboard was on Nov 7, 2026.
What can I use JapaneseKeyboard for?
Typing Japanese on Android without sending keystrokes to a cloud service. Keeping a personal dictionary and frequently used phrases that can be backed up and moved between devices. Building a keyboard layout tailored to one's own typing habits. Using a Japanese keyboard on tablets or foldables.
How do I install JapaneseKeyboard?
Install the app from Google Play, F-Droid (Lite build), or the GitHub releases page In Android settings, open the on-screen keyboard list and enable Sumire Clone the repository to build from source: git clone https://github.com/KazumaProject/JapaneseKeyboard.git Build and install the debug app on a connected device or emulator: ./gradlew installDebug
Where can I get JapaneseKeyboard?
The source code and installation instructions are on GitHub: https://github.com/KazumaProject/JapaneseKeyboard

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