User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:51.0) Gecko/20100101 Firefox/51.0 Build ID: 20170126200443 Steps to reproduce: I would like to be able to create silent WebExtension notifications so that I can trigger my own audio file for a consistent experience on all platforms. On Linux, Firefox doesn't automatically trigger the desktop environment notification sound. On Mac, Firefox does automatically trigger the desktop environment notification sound. Since my addon acts as a timer, a notification as well as a notification sound is highly useful. The problem is that if I play a notification sound when the notification is created, the MacOS notification chime plays on top of my own notification sound. https://developer.mozilla.org/en-US/Add-ons/WebExtensions/API/notifications/NotificationOptions I imagine the option would very similar to the silent option for the Web API notifications: https://developer.mozilla.org/en-US/docs/Web/API/Notification/silent.