I want to share some dynamic content on google+. For this I checked it https://developers.google.com/+/web/share/interactive#rendering_the_button_with_javascript
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I same had the problem for google + api sign in.I was getting Error:origin_mismatch and same details were there as they are in the question .. my javascript credentials had http://localhost:4567 but when I run the python file it opened the link as 0.0.0.0:4567 thats basically a localhost but when i changed the url in browser to http://localhost:4567 now the error was removed .. and my application was able to get the OAuth box .. and all went fine!!! this thing removed my error... Please let me know whether I was correct because I just started learning how to use apis