Enable developer console in browser and navigate to:
Look for the response of POST request in the network tab of developer console: https://www.facebook.com/v2.6/dialog/oauth/confirm?dpr=1 it contains the access token parameter. Just search for 'access_token' in the response. For the lazy people (like myself) i made a small helper that parses the token from response https://taseppa.github.io/tokenparser.github.io/
@FavyTeam cold you describe the process in a more detailed way? For example in which tab of the developer tools and if we have to click ok on the prompt or not. It's ambiguous as it is written now, thanks.