Google OAuth 2 authorization - Error: redirect_uri_mismatch

Question

On the website https://code.google.com/apis/console I have registered my application, set up generated Client ID: and Client Secret to my a

Answer 1

for me it was because in the 'Authorized redirect URIs' list I've incorrectly put https://developers.google.com/oauthplayground/ instead of https://developers.google.com/oauthplayground (without / at the end).