Create a Spotify App & Add a Redirect URI

1. Go to the Spotify Developer Dashboard → create an app. https://developer.spotify.com/dashboard

2. In the app Settings, add a Redirect URI you can receive in a browser, http://127.0.0.1:8888/callback, then Save. 

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2) Authorize your account (one-time)

Open this URL in your browser (replace YOUR_CLIENT_ID and URL-encode the redirect URI):

https://accounts.spotify.com/authorize?client_id=YOUR_CLIENT_ID &response_type=code &redirect_uri=http%3A%2F%2Flocalhost%2Fcallback &scope=user-modify-playback-state%20user-read-playback-state &state=xyz123

• Log in, approve. Spotify will redirect to:

  http://localhost/callback?code=AUTH_CODE&state=xyz123

• Copy the code value. (Those scopes are what you need to transfer/play/pause and to read device status.)