Dropbox API V2 Sign out

Ah, I think maybe I understand.

1. A user clicks the "log in" button in your app.
2. You take the user through the OAuth flow in the browser (since the Dropbox app is not installed).
3. If the user isn't already logged in to the Dropbox website, they'll need to enter their username and password to log in.
4. Now a new user on the same device wants to log in to your app. But the previous user is still logged in on the Dropbox website.
   

So you want to programmatically log the user out of dropbox.com. This is not something you can do via the API, since in general, users don't want apps to be able to log them out of their browser sessions.

That said, you can always send the user to https://www.dropbox.com/logout, which will log them out in the browser, but it won't return the user to your app.