The Spotify app has the ability to automatically adjust your audio stream to match on your internet connection speeds. But if you are concerned about your mobile data consumption or experiencing a slow internet connection, you can adjust Spotify's default streaming quality (bitrate) to your liking.
How To Set the Default Streaming Quality on Spotify
Open the Spotify app and go to Settings > Streaming Quality. Audio streaming quality is set to Automatic by default, but there are other presets for you to choose from: Normal (96 kb/s), High (160 kb/s), or Extreme (320 kb/s).
You will drastically reduce your mobile data consumption by switching to the Normal mode.
N.B. The Spotify app also allows you to sync your songs so that you can listen to them offline. If you would like to enable this feature on your mobile, please read our article Offline Music with Spotify.