I just installed the "Last.fm Scrobbler" and while everything seems to work fine I was confused by not finding the extension's toolbar icon. Apparently the extension is using the page action menu (page context menu!?), and icons (depending on scrobbling status) will be displayed, but only a) on particular websites, i.e. https://play.google.com/music/listen or https://tunein.com/radio/home/ b) while a track is playing, i.e. Youtube music video or Vimeo videos The extension's FAQs will soon inform their users about the positioning of the icon. Due to the fact that page action menu can be hidden like in this example, it would be a better experience IMHO, if there would be a possibility for extension developers to display a notification upon or after installation to display together with the icon.

Chrome after installation shows notification sticked to extension icon, right? Similar in Firefox would be nice, for page actions it should be displayed when icon is 1st time visible, eg.:

The extension can also show any sort of notification of its own on install explaining how the extension works.

Hey Andy, I now have the situation where I have a gap between two page action icons and was wondering why until I realised that the empty spot is for the last.fm scrobbler which is visibly hidden on unsupported pages. Is the idea to have a icon in a disabled state provided by the extension, or is Firefox currently simply hiding the icon?

That sounds like a seperate bug. There's been some changes to page actions recently in Firefox 58, what version are you on?

Those screenshots were taken with the latest 58.

As of today - just restarted with an update 10 minutes ago - there is now a default extension icon as a placeholder instead of nothing.

Thanks, that was bug 1413648.