Version: Smart Feature Phone 3.0


The simulator lets you run Gaia and Web apps in a Gecko-based environment somewhat similar to an actual device. It doesn't emulate device hardware, so it's not adequate for testing device APIs and it isn't a replacement for testing on actual hardware. It can, therefore, be useful during the development of your application, or while working on the application user interface itself. This article covers downloading of the simulator, as well as how to use it.


Release information

Revision: SFP_3.0.0-kaiosrt_next-ubuntu-20210708154941-n128 (July. 2021)

Release note:

  • 1st release on KaiOS 3.0

Launch KaiOS Runtime (Kaiosrt) app


We only support ubuntu 18.04 for now, please make sure you use this version.

Run Kaiosrt
  • Then you will see the Simulator's window
KaiOS 3.0 Simulator

Install Firefox and web extension

Download and Install FireFox Nightly

  • Download Firefox Nightly from

  • Make sure you get the same version as kaiosrt. (currently is 84)

  • Launch Firefox Nightly and enter: about:debugging#/setup in URL bar

  • In Network Location section, Add Host localhost:6222

  • Connect to localhost:6222

  • Select localhost:6222 and you can see apps Tabs

  • Inspect your app

  • Start debug

Install web extension - KaiOS DevTool

  • Ubuntu (tested with 18.04)
  • Python (tested with 2.7)
  • Firefox nightly tested with 84.0b4
Installation Steps:
  1. Download latest artifact from here and unzip it.

    • Or clone the repo then execute npm install && npm run build.
    • For MacOS/Windows, please replace executable dist\app\appscmd with the correct one under dist\app\target\<environment>\appscmd(.exe)
  2. Open terminal, execute the following shell command to install native messaging app.

    cd dist
    bash app\

    For Windows please make sure python installed then execute following steps

  • Rename message_host_win.json to replace message_host.json
  • replace %~dp0 inside install_native_app.bat and message_host.bat to valid path
  • execute install_native_app.bat
  1. Make sure KaiOS device connected with adb root, seems appscmd crashes without this.

  2. Open firefox nightly & go to page about:debugging

  3. Click This Nightly on top left

  4. Title Temporary Extensions, click Load Temporary Add-on, choose manifest.json.

  5. Click terminal icon on toolbar.

  6. KaiOS-DevTool UI is shown

Create a new app

Please refer to Sample code

Install and uninstall an app

Install an app using appscmd on Simulator

  1. Launch KaisOS Runtime Simulator
  2. On Seperate Terminal cd to appscmd folder
  3. Run to install on Simulator
    ./appscmd --socket /tmp/apps_service_uds.sock install /your_app_path

    Note: Dependency needs to removed from manifest file for the app to work on Simulator.

Install an app using DevTool

  1. Click on the Install App button
  2. Choose an app

Uninstall an app

  1. Find the app and click the remove button in the right

Debugging runtime apps