I think they don't do this anymore. I have some old playlists with some tracks greyed out so I think that's their new way of dealing with songs they no longer have rights to let us play.

I believe there's a setting somewhere in your account to turn this on, I think by default it just hides tracks that have been removed from the service. They stay there on the playlist (I guess in theory if the track comes back onto the service it'll reappear, but in practice I've found it's often a slightly different version that doesn't get matched up).

There's also a bit of explanation about this at https://developer.spotify.com/documentation/general/guides/t...

ye I noticed they swap them sometimes as well. which i hate. i'm really picky about that. Even slightest difference to the version I like can make me hate any other version. so getting one slightly faster from another album is no good for me.

You are right, I have enabled it myself.

They don't do that anymore: unplayable songs are greyed out, but they still show on playlists.

It would be great to get notifications when this happens, though.