I'm currently testing an integration of Spotify OAuth with my NextJS app. I've found that, after whitelisting the redirect URL under the developer dashboard, the localhost version (i.e. localhost:3000/api/auth/spotify) can successfully redirect the user after authenticating with spotify, but the live version will always lead to an OAuth error for some reason. I've double checked the redirect URL when the user tries to authenticate through the live app (i.e. &redirect_url=....) and double checked many times to make sure I didn't miss any backslashes or misspell the link when adding it to the list of redirect URIs. Can someone help me understand why that is? Thanks so much!
Awesome to hear that you're moving your development app into a live environment. Can you describe the error further that you are seeing? Is an error message being displayed? If the app is publicly available then feel free to post a link to it here as well.