If you're a Spotify Premium user, you can download songs for offline listening. To do so, open the Spotify app and sign in to your Premium account. Then, go to My Library and tap the playlist or album you want to download. You'll see a down arrow next to each song that will be downloaded.
On the desktop, you can only download playlists, not albums or podcasts. Unfortunately, it's not possible to download a single song using the conventional method mentioned above. However, there is an alternative solution for downloading a single song. To use it, you'll need to create a playlist with just one song in it and then follow the steps above. To get the most out of Spotify music downloads, there are a few tricks you can use. For example, you can download single episodes of podcasts or follow a specific podcast and download the episodes as they appear in your library.
Additionally, you can use offline mode to make sure that only downloads are playing when you lose Internet. If you no longer need offline access or want to free up space on your device, navigate to the album or playlist that you want to remove from downloads and deactivate the Downloaded button (Android) or tap the green arrow that points down at the top left and tap Delete in the pop-up window (iOS).