This project was developed with the sole purpose to help users get the data they need. It started when I (Makan) wanted to find a way to view statistics of the music we listened to in the past. Spotify itself doesn't have an option to view stats, and the other websites up right now are either too simple or require too many permissions. This website checks off all the boxes, an interactive website with no requirements to access sensitive data to your account. The code to the first version of mySpotify is up on GitHub to view. Most of the code from this website is built directly off the open-source version.
To provide more information on the history of account statistics, we save the information of your top tracks and artists in a database. Upon sign-up, we record your username (so we know how to show the data to you and not anyone else) and 48 tracks/artists from your history. We do this every 12 hours because Spotify only provides us information every once in a while, alongside the fact that our servers aren't that powerful to support millions of rows of data. Your access token is never saved on our system, it's saved as a cookie on your device. This means we don't have access to your data when you're not on the website, so the only time you can update your stats is when you visit the website. Even though Spotify says we have access to your email, profile picture, etc, this data is not ever recorded in our system - we're required to get access to that data due to the scope we request from Spotify.
To simply answer, we don't. Right now all server monitoring and hosting is done out-of-pocket, and the development is done under my company: SyntxProject (which I am the owner of). In the future, we are looking towards expanding the information we can provide by possibly a small subscription or the ability to promote songs, but that's for way further in the future. Right now, this is just a fun development project I enjoy working on.
Of course! You can view all the data we have stored on your account at your account page. Hitting the delete button actually does delete all your data. It doesn't go into an archive or some secret section of our server. Once it's gone, it's gone.