Logging in with an account other than mine returns 403.

[dogages]

Currently Spotify does not allow sharing saved song lists, so I deployed an app in Vercel that converts saved song lists into a new playlist.

URL : https://spotify-playlist-splitter.vercel.app/

When I log in with my account, the various APIs return 200, but logging in with a friend or family member's account and making an API call returns a 403 error.

Is this a issue that happens because I'm in developer mode?

If that's the reason, it's for hobby use, but I'd like to publish it on Twitter, so I'd like to switch to quota extension mode.

Client ID 31c6d25d3954406bbf1fa25ce801b4db

The API and scope are these

APIs

- GET https://api.spotify.com/v1/me

- GET https://api.spotify.com/v1/me/tracks

- POST https://api.spotify.com/v1/playlists/playlist_id/tracks

- POST https://api.spotify.com/v1/users/user_id/playlists

Scopes

- user-library-read

- user-library-modify

- user-read-private

- playlist-modify-public

I used DeepL to post this topic. Sorry if I didn't make sense.

[Ximzend]

If you are in developer mode, you have to add their Spotify Accounts (full name and email address) to the developer dashboard of your app under Users and Access (click the button and scroll) before they can use your app.