Facebook Developer App Id. At the right corner of the top navigation bar, click the my apps link and select add new app. Then click on create app id button to create your app same as below screenshot displayed.
To get an app id, follow these steps. Enter the display name and contact email. Go to facebook developers site and click on “register now” green button to sign up as developer to create a new app.
You need these credentials to do almost anything with facebook, including going through the oauth authorization flow and working with facebook's graph api.
The reason why all the domains running on tumblr are validating fine with a single app_id, is that the facebook debug tool only checks the validity of the og_tag's structure (at least when it comes to the app_id). Go to facebook developers site and click on “register now” green button to sign up as developer to create a new app. Visit the facebook developers page To get an app id, follow these steps.
