1. Download/clone this repo to your machine
2. Open chrome://extensions and click Load unpacked extension...
3. Browse to the downloaded folder and click Select

1. Download/clone this repo to your machine
2. Open about:debugging and go to This Firefox. After that click Load Temporary Add-on...
3. Browse to the downloaded folder and click Select

To improve speed of sending value to server, it is a good idea to play around testServerConnection function interval value, since it is how often, extension should check if server is online, for now it is set to checkInterval variable.