Mostly yes, but there are exceptions. Genre specific sites will only post music in their respective genre. For example, BeatPort is a site that specializes in Electronic Music would not post Classical or Heavy Metal music on its site. And there are a few retailers, such as Pandora, that do make the final decision regarding which projects they make available. However, rest assured that your music will be available on all major, non genre-specific sites (such as iTunes, Amazon, Apple Music, Tidal, Deezer, Juno Download, Spotify, etc.).