Next.js 14 oAuth 2.0 authorization flow redirect 401 error

So both of my replies seem to have been deleted. I would be grateful if I could understand why that was.

I appear to have solved the issue, with the hurdle being a conceptually different understanding to what the redirect url was meant to represent.

I originally had the redirect url representing an api route in a Next.js 14 app using the app router.

When I had a moment of differentiation, I changed the redirect url to the client side page from which the authorization process had commenced (the clicking of a button) (SOURCE PAGE); although the GET 401 error still appeared in the console, after about 1 second of a blank browser, the SOURCE PAGE did appear, with the url containing the code obtained from the authorization flow. Once this was accomplished, it was a matter of grabbing the code from the url, and then passing this to the api route which swapped this for an access token.

So, I guess, when @Greg-DB said I " need[ed] to check on what it is doing on its /api/dropboxcallback page" in essence he was right, but it took some time to understand what essentially he meant by this - which is, as is my current understanding, this should not be an api route, rather a client-side page from which the code in the url can be obtained, and then sent to an api route to exchange for an access token.

I appreciate there are a few examples of how this oauth process works, with working code examples, but as I presume this is meant to be deployed in a front end application, it would be good to have at least one example of how it is meant to be used in a front end framework (of some language) and not just in node.js.

However I got here, I am very glad it appears to be working.