In a post published about the topic yesterday by user riegelstamm, it was pointed out that Spotify's system requirements page listed Safari 6 or higher as a supported browser for the Web Player. As of today, that same page has been updated and any mention of Safari has been removed, now only including Chrome 45+, Firefox 47+, Edge 14+, and Opera 32+.
When users visit the Spotify Web Player on Safari, they receive the message, "This browser doesn't support Spotify Web Player. Switch browsers or download Spotify for your desktop."
The same poster contacted Spotify customer support, which responded with a confirmation of Safari's removal from the Web Player's supported browser list.
"After taking a look backstage, we can confirm that after recent updates Safari is no longer a supported browser for Web Player. We're always testing things by adding or removing features to make Spotify better overall. We’re sorry that this means you’re not able to use the Web Player like you could before. We can't say if or when any specific features will be back. But as soon as we’ve got anything to announce, we’ll let everyone know via the Spotify Community. Sorry again for any inconvenience caused, and please let us know if there is anything else we can do for you.Riegelstamm further dug into the details of the Web Player, discovering that the discontinuing of Safari support might have something to do with Google's Widevine media optimizer plugin, which Spotify requires for music streaming on the web and Apple opposes due to potential security issues.
Spotify Customer Support"
Instead, Spotify encourages users to download the compatible Mac app, or switch over to a supported browser. Although the lack of Safari support in the Web Player might be temporary, Spotify customer support told users that it "can't say if or when any specific features will be back."