How can I download playlist from spotify to mp3 on my computer

First, let's be clear about the legal and technical situation for downloading playlist from Spotify:

Spotify's Official Way: With a Spotify Premium subscription, you can download playlists, albums, and podcasts within the Spotify app for offline listening. This is not MP3 files; it's a protected, encrypted format that only the Spotify app can play. You cannot transfer these files to an MP3 player or another music program.

The "Unofficial" Way: To get actual MP3 files, you need to use a third-party Spotify music downloader tool. These tools record the audio stream from Spotify and  save it into an MP3 file. The legality of this varies by country and is generally accepted by Spotify's Terms of Service. It is typically for personal, fair-use purposes only (like having a backup of a playlist you already own or for a device that can't run Spotify). 

For most users looking for a balance of ease and reliability, a dedicated Spotify playlist downloader is the most common recommendation, despite the cost. If you are technically inclined and want a free solution, the command line tool is the community favorite. However, online service is generally advised only for grabbing one or two songs quickly, with extreme caution.

Always remember to support the artists you enjoy by buying their music or merchandise whenever possible!