Based on Chrome Extension sample from Google's Getting Started guide.
Documentation here.
This version of the code is as rewriting of the original Google example using Kotlin. The API has been extended using Kotlin Coroutines. The extension code has been modified to use coroutines APIs. The API was converted to use Browser Extensions W3C proposed standard. Original comments have been kept at the closest place of the original code.
- Original version in JavaScript here.
- Initial rewrite in Kotlin here.
- Extension with Kotlin Coroutines only for Chrome here.
Please check this series in Medium that describe this project:
- Writing a Chrome extension in Kotlin
- Writing a Chrome extension in Kotlin — Using Coroutines
- Writing a Chrome extension in Kotlin — Supporting Firefox and Chrome
This project uses gradle. To build it, execute the following:
gradlew clean assemble
Unbundled extension will be generated inside build/extension.
This folder can be used to install in Chrome.
Zipped extension will be generated inside build/distributions.
The zip generated inside that folder can be used to install in Firefox.
- Go to Extensions
- Enable "Developer Mode"
- Click on "Load unpacked extension..."
- Select the folder
${project}/build/extensionand open it.
If changes are made and the extension is recompiled, make sure to update the extension:
- Go to Extensions
- Make sure "Developer Mode" is enabled
- Click on "Update extensions now"
Make sure to check Google documentation for more details.
The extension needs to be uploaded to Mozilla Add-ons website for the extension to work in Firefox.
Please follow instructions here.
Upon installation a a new extension is added to Chrome/Firefox with the icon 
Clicking the icon will open a small popup that will allow changing active page background color.
Check Google's Getting started guide for more details.