From the Terminal
How to make a launcher for Spotify in Linux that works with Spotify links
When launching Spotify in Linux by default the deb package comes with a desktop file that contains an exec that essentially just runs the "spotify" binary. Spotify does have a dbus interface for certain things. We can look for an existing process and if one is found we throw the Spotify link into dbus instead of opening another Spotify instance.
I wrote a simple launcher replacement. Just set your desktop file to use this instead of the default.