This extension switches tabs between Spotify's Web Player and the most recently open tab.
The use case for this extension is simple:
I've often got 10+ tabs open, sometimes in several Chrome windows. If I'm listening to a song in the Web Player and I want to skip a track or add the currently playing track to a playlist, I need to make a quick context switch to find the tab holding the Web Player, do what I need, and find the tab I was working in again. This isn't a problem if you're just doing it once or twice a day. But if you're fortunate enough to listen to music several hours every day, the pain adds up.
This operation is done easily on the desktop client. Just Alt+Tab to Spotify and Alt+Tab back to Chrome. What this extension tries to do is to make the same switch as quick as when using the desktop client, or maybe even quicker.
Click on the extension icon or use the keyboard short-cut (Command+Shift+S on Mac OS X, Ctrl+Shift+S on Windows/Linux/Others) to toggle between the Web Player and the tab you're working in. Clicking on the icon once will open the Web Player, and clicking it again will take you back. It doesn't matter if the Web Player is in a different Chrome window, toggling will switch windows as well.